Getting Started

To get started with VOSviewer, you may want to take a look at some of the sources of information listed below.

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VOSviewer manual

The VOSviewer manual provides detailed and up-to-date information on the functionality of VOSviewer. The manual can also be accessed using the Manual button in VOSviewer.

Open VOSviewer manual

 

VOSviewer book chapter

VOSviewer is discussed in detail in a recent book chapter. The chapter provides a tutorial in which the use of VOSviewer is demonstrated in a step-by-step manner. The chapter is based on VOSviewer version 1.5.5. Some of the improvements and extensions introduced in the most recent versions of VOSviewer are therefore not covered in the chapter. In addition to VOSviewer, the chapter also discusses the CitNetExplorer tool for visualizing and analyzing citation networks of publications.

Open VOSviewer book chapter

VOSviewer paper

VOSviewer was originally introduced in a paper published in Scientometrics in 2010. In the meantime, VOSviewer has been improved and extended in many ways, so the paper is not fully up-to-date anymore. However, it still provides a useful introduction into the main ideas underlying VOSviewer.

Open VOSviewer paper

AIDA bookletAIDA booklet

The AIDA booklet introduces diverse case studies on research positioning and trend identification. These case studies are relevant for PhD candidates, researchers, group leaders, and policy makers. Many of the case studies make use of VOSviewer.

Open AIDA booklet

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  • Maria P. April 17th, 2018 12:01 pm
    I am interested in making a co-authorship map with data downloaded from SCOPUS. I have seen this option is not supported for the current vosviewer version. Is there a way of downloading the 1.6.5 version? The reason I want to use SCOPUS data is that I can easily download all articles from the institution where I work from SCOPUS (we have an scopus institution ID, and all our articles are associated) but not with Web of Sciences (researchers write the affiliation address in too many different ways). thanks!
    Reply
    • Nees Jan van Eck April 19th, 2018 10:32 pm
      VOSviewer version 1.6.5 can be downloaded using the following links:
      Windows: http://www.vosviewer.com/download/f-y2t2.zip
      Mac: http://www.vosviewer.com/download/f-y2v2.zip
      Other systems: http://www.vosviewer.com/download/f-y2u2.zip
      Reply
  • Amin April 6th, 2018 1:27 pm
    Dear Ludo,
    I am having difficulty with the export from web of knowledge to VOSViewer. When I choose "export to other formats" --> "records (1-269)"--> "Full record and cited references" --> "tab-delimited (win)" --> "Send"
    Then in the software I try to "create a map based on the bibliographic data" --> --> in the web of science tab I choose the text file---> citation -document
    Then instead of the number of 269 records I end up with 219.
    I tried to extract info to Endnote and indeed the number of records are 219!
    I am puzzled of why from 269 records in Web of knowledge only 219 show up in the export process.
    If I export " "Full record" then it comes with 269 records.
    However, then I cannot make a citation document map. Do you have any suggestion?
    Reply
    • Mihaela April 6th, 2018 10:52 pm
      Hello Amin,
      I recently tried to work with web of science and I am having similar problems with "Full record and cited references". It either exports a empty tab-delimited, one were first column headers are "null", completely missing headers, or in the happy event were everything is ok some records missing. I think its a wos problem at export. I managed to work around by exporting batches of 6-14 articles at a time, but its hard work and i only have around 200 articles. I cant imagine doing the same with a large sample of articles.
      To note that a few months ago everything worked ok.
      Reply
      • Amin April 7th, 2018 7:16 am
        It also worked for me few months ago. I tried to extract them in smaller batches of 50. I would do it with what you suggested. Many thanks.
        Reply
        • Ludo Waltman April 7th, 2018 7:22 am
          I'll do some further investigation of this problem. As a temporary workaround, my suggestion is to export data from Web of Science in plain text format instead of tab-delimited format. VOSviewer also supports the plain text format.
          Reply
          • Amin April 7th, 2018 9:43 am
            Dear Ludo
            I I tied and an error returned
            Error while reading web of science file File is invalid
            Reply
            • Ludo Waltman April 7th, 2018 10:28 am
              Amin, Mihaela, could you please send some examples of invalid files to vosviewer@cwts.leidenuniv.nl? This will help me to investigate the problem. Thanks!
              Reply
              • Amin April 9th, 2018 11:33 am
                Dear Mihaela and Ludo,
                I tried to export records in smaller batches of 10. However, it seems the problem still persists. I figured out that some of the records have a value of (null). So, I miss some of the information on the citation data for some of the results. The only thing that I can do is to skip that particular record. Michaela: Can you confirm that this also the case for you?
                Reply
                • Ludo Waltman April 9th, 2018 12:02 pm
                  Brief update: It is clear now that the problems occur both in tab-delimited files and in plain text files. Indeed, as indicated by Amin, one of the problems is the appearance of 'null' strings in the files. Another problem relates to records that are missing in the files. I am in contact with the Web of Science team and they are investigating these problems.
                  Reply
                  • Amin April 9th, 2018 12:33 pm
                    Dear Ludo,
                    In my search I found out that only two records are missing (as null). However if I want to export at once then from 269 only 219 records would be there. Somehow it seems that Web of Knowledge export function does the job in batches. So, if in one of the batches there is a NULL record then the whole batch comes at NULL. In my search records 74 and 210 are NULL. I cab send you the search phrase if needed.
                    Reply
                    • Mihaela April 11th, 2018 2:11 am
                      Sorry for not giving feedback, i was out of town for hollyday. I will send some examples to you Ludo. Amin i suspect the same, batches download. I started with larger batches and then downscaled. In some parts i had to take the articles one by one, and in the end i am only missing around 10 articles out of 250. But i had the whole list of titles downloades before so i searched after the title.
                      Reply
                      • Ludo Waltman April 19th, 2018 7:58 pm
                        Clarivate Analytics has informed me that the problem with the Web of Science export has been fixed. If you still experience difficulties, please let me know.
                        Reply
                        • Mihaela April 19th, 2018 8:01 pm
                          Thank you Ludo,
                          I will try as soon as possible.
                          Reply
  • Patrick Zawadzki March 31st, 2018 5:50 pm
    Hello Ludo! Congrats for this great software, you are doing a great job.
    We just started to use it and found problems on how to do some interpretation.
    When using co-ocurrence of authors keywords some networks shows keywords from different clusters, if the cluster is a correlation between keywords why this happens?
    Cheers
    Reply
    • Ludo Waltman March 31st, 2018 10:03 pm
      I am afraid I don't understand your question. What do you mean by "some networks shows keywords from different clusters"?
      Reply
      • Patrick Zawadzki April 17th, 2018 1:43 am
        For example, we found a network with three nodes, first and second nodes are inside red cluster, and, the third node is inside blue cluster. Our analysis is looking for associated keywords in a specific new area, it is better to use the cluster ou the network results as parameter to decide better association?
        PD: sorry about my poor english.
        Reply
        • Ludo Waltman April 17th, 2018 2:46 pm
          The network structure offers the most detailed information about the way in which keywords relate to each other. The clustering provides a simplified picture by assigning each keyword to a single cluster. Indeed this means that sometimes different items are assigned to different clusters even though the items are linked to each other. The clustering technique used by VOSviewer tries to assign items to clusters in such a way that the number of links between items that are in different clusters is minimized, but there will always be some links that connect items in different clusters.
          Reply
  • Tanya March 26th, 2018 5:24 pm
    Hi VOSviewer (and thanks for the wonderful support you provide here!),

    I'm trying to launch VOSviewer through the command line to increase available memory. I've downloaded the .jar file and run the code 'java -Xmx1000m -jar VOSviewer.jar' in terminal, however before VOSviewer launches I get a very long error, starting with:

    Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at org.pushingpixels.substance.internal.utils.SubstanceColorUtilities.getDefaultBackgroundColor(SubstanceColorUtilities.java:759)

    I'm not sure how to proceed from here..? Thanks!
    Reply
    • Ludo Waltman March 26th, 2018 6:22 pm
      Most likely, this error is caused by the fact that you are using Java version 9. Unfortunately, VOSviewer currently cannot be run using Java version 9. You need to use version 8 of Java. In the future, we of course hope to make VOSviewer compatible with Java version 9, but this requires some significant technical changes to be made to the software.
      Reply
      • Tanya March 27th, 2018 4:32 pm
        Ah, thanks! I had installed JDK10 in order to run the java command in terminal. I switched to JDK8 and was able to expand the memory with no problems.
        Reply
  • Antonio February 26th, 2018 2:27 pm
    Hello Ludo.
    I've just updated to new version 6.7, but now I cannot generate the network of authors according to their bibliographical coupling. The option "author" is not avaible anymore, but "documents", "sources", "organizations" and "countries" are still available. When I try to identify the authors by their "documents", all them appear as "anonymous".
    I tested with the same .txt files extracted from Web of Science in the 6.6 version and it worked well.
    Thanks for this powerful software!
    Reply
    • Antonio February 26th, 2018 2:42 pm
      Just a correction: this problem occurs when I export the results from SciELO Citation Index (a Web of Science collection). But the same .txt file works well with 6.6 version.
      Thanks again!
      Reply
      • Ludo Waltman February 26th, 2018 3:40 pm
        Could you please send your file to vosviewer@cwts.leidenuniv.nl? I will then take a look at it. Thanks!
        Reply
        • Ludo Waltman February 26th, 2018 11:12 pm
          Thanks for sending your file. In VOSviewer 1.6.7, we changed the way in which author data is extracted from Web of Science files. This was done in order to be able to process first names of authors. The new functionality was tested for data downloaded from the Web of Science Core Collection. We did not perform any tests for the Web of Science SciELO citation index. VOSviewer 1.6.7 indeed turns out to be unable to extract author data from Web of Science SciELO files. We were not aware of this, and we will try to fix this problem in the next update of VOSviewer. As a temporary workaround, you could use VOSviewer 1.6.6 for creating maps of authors based on Web of Science SciELO files. Alternatively, in your files, you could change the header 'AU' into 'AF'. By changing the header, VOSviewer 1.6.7 should be able to process your files. Thanks a lot for drawing our attention to this issue.
          Reply
  • Sven Januszek February 22nd, 2018 2:44 pm
    It seems as if the bug from Scopus has not been fixed yet. I am still facing problems using my CSV files from Scopus. It says: Error while reading Scopus file "XXX" (line: 5974): Incorrect number of coumns.
    Reply
    • Kirsty February 22nd, 2018 2:51 pm
      Yes it is unfortunately - apparently Scopus have said it should be fixed by the end of the month...
      Reply
    • Ludo Waltman February 22nd, 2018 5:02 pm
      Indeed the problem has not yet been fixed. The Elsevier Scopus team is still working on it. They expect the problem to be fixed by the end of the month.
      Reply
      • Ludo Waltman February 23rd, 2018 9:31 am
        I have just been informed by the Elsevier Scopus team that an update of Scopus will take place on Wednesday February 28. This means that on Thursday March 1 the problems with the Scopus CSV export should be solved.
        Reply
        • Ludo Waltman March 1st, 2018 10:50 am
          I have just performed some tests with the Scopus CSV export. It seems that the problems have been fixed. If anyone is still experiencing problems, then please let me know.
          Reply
          • Sven March 2nd, 2018 9:28 am
            Seems to still not work for me. I exported the CSV file from Scopus this morning and still get the error message: "Error while reading Scopus file 'XXX' (line 9711): Incorrect number of columns.
            Maybe my excel sheet is just too large with almost 10k rows.
            Reply
            • Ludo Waltman March 2nd, 2018 9:43 am
              Could you please send your file to me (vosviewer@cwts.leidenuniv.nl)? Thanks!
              Reply
              • Sven March 2nd, 2018 9:59 am
                I sent you the files and hope the mail attachment was not too big. Please let me know if you still have not received the mail.
                Reply
                • Ludo Waltman March 2nd, 2018 4:43 pm
                  Thanks Sven for sending me your files. I have taken a look at them.
                  Scopus has two options for exporting CSV files, an option ‘CSV - Only the first 2,000 documents’ and an option ‘CSV - Export all documents to a CSV file, citation information only’. It seems that you have used the second option, which apparently still suffers from a bug. I will report this to Elsevier. However, my recommendation is to use the first option. Your CSV file will then include more data per document, so that you have more options in VOSviewer for creating maps. It seems that the first option does not suffer from bugs anymore. If you experience any problems with this option, then please let me know.
                  Reply
                  • Sven March 5th, 2018 9:01 am
                    Thanks a lot Ludo!
                    Indeed the first option works out for me. Unfortunately, I would have to use more than just 2000 entries for my analysis. Hopefully, the second option will get fixed soon by Scopus. In case you hear anything from them, it would be nice to get an update from you.
                    Cheers,
                    Sven
                    Reply
                  • john March 13th, 2018 11:22 am
                    Hi,
                    Unfortunately, I'm still not able to generate a map in VOS Viewer based on a Scopus CSV output file. The program reports: Incorrect number of columns. Is this somehow related to the previous reported bug? Or maybe I made a different mistake?
                    Kind regards,
                    John
                    Reply
                    • Ludo Waltman March 13th, 2018 12:36 pm
                      I am sorry to hear this, John. Could you please send your file(s) to vosviewer@cwts.leidenuniv.nl? I will then take a look at them.
                      Reply
  • Christian February 18th, 2018 12:44 pm
    How are the total link strengths calculated?
    Reply
    • Ludo Waltman February 18th, 2018 1:50 pm
      This is explained in the VOSviewer manual. If the explanation provided in the manual is insufficient, then please let me know.
      Reply
      • Peter Frappell February 21st, 2018 7:30 am
        Hello Ludo -
        I get the "Links" attribute it is directly related to the number of co-authorship linkages, but I am also unsure how you weight the "Total Link Strength" attribute, could you please explain.
        thanks, Peter
        Reply
        • Ludo Waltman February 21st, 2018 6:12 pm
          Let me try to clarify this by providing a simple example. Consider an author A. Suppose author A has 4 co-authored publications with author B and 5 co-authored publications with author C. Author A then has co-authorship links with two other authors, and therefore the total number of links of author A equals 2. The total strength of these links equals 4 + 5 = 9. I hope this clarifies the distinction between 'links' and 'total link strength'. Please let me know if it is not yet sufficiently clear.
          Reply
          • Peter February 21st, 2018 10:36 pm
            This simple example makes it perfectly clear, Perhaps the definition in the manual could be reworded:
            “Links” - number of co-authors
            “Total link strength” - ithe sum of the number of links with each co-author.
            Thanks for the prompt reply.
            Reply
  • Stephane ledoux February 14th, 2018 11:39 am
    i've been trying to process a larger than usual set of data and failed, i've try to increase the memory allocation by using the command line java -Xss1000k -jar VOSviewer.jar after i've downoaded the Vosviewer.jar file it has indeed open vosviewer but the allocation was stuck to 247mb it is even lower than when i used vosviewer 1.6.6 directly (989 mb)
    Reply
    • Ludo Waltman February 15th, 2018 4:53 pm
      You need to use -Xmx instead of -Xss.
      Reply
  • Ka Pauw January 24th, 2018 3:32 pm
    Hi,
    How do you generate different variations of the term map with regard to journals, countries and open access?
    I have noticed this feature in your presentation "VOSviewer: A software tool for analyzing and visualizing scientific literature" [Sep 14, 2017] page 11-13 on SlideShare, but when I "Create a map based on text data" based on Web of Science files I do not see any options in the interface to associate the coloring with any underlying data attributes.
    Thanks for a very practical and yet powerful piece of software!
    Reply
    • Ludo Waltman January 24th, 2018 5:33 pm
      When creating a term map based on Web of Science files, these options are indeed not available. Instead, you need to create a term map based on a VOSviewer corpus file and a VOSviewer scores file. This means that you need to do some preprocessing of your data. You need to concatenate the titles and abstracts of the publications in your Web of Science files and you need to save the concatenated titles and abstracts in a corpus file. In addition, you need to create a scores file, with scores indicating whether a publication has appeared in a specific journal, whether it has been authored by a specific country, or whether it is open access. Creating the scores file can be a bit more complex. More information about scores files is provided in the VOSviewer manual.
      Reply
  • Sri Amudha Kumaresan January 13th, 2018 3:47 am
    Hello! Thank you so much for sharing this wonderful software. I'm using this software in my research for cluster analysis. I have done my work in version 1.6.4 and due to technical difficulties I have lost it. Now, I'm unable to download the same version. Can you please share me the version 1.6.4?
    Reply
    • Nees Jan van Eck January 15th, 2018 9:46 am
      VOSviewer version 1.6.4 can be downloaded using the following links:
      MS Windows: http://www.vosviewer.com/download/f-x2z2.zip
      Mac OS X: http://www.vosviewer.com/download/f-y2r2.zip
      Other systems: http://www.vosviewer.com/download/f-y2q2.zip
      Reply
  • Theoni Paschou January 1st, 2018 5:23 pm
    Good afternoon and a happy new year,
    I saw your software applied to another literature review (Zhang, 2017) and I am also interested in it but I face some difficulties importing the data.
    Can I import them also from excel? I have the Impact factor, number of citations, year etc.
    Otherwise would you mind supporting me so to import the data from Scopus?
    I would truly appreciate your kind help.
    Best,
    Theoni
    Reply
    • Ludo Waltman January 2nd, 2018 11:45 am
      If you want to provide your own data as input to VOSviewer, this can be done using VOSviewer map and network files, which can be created using Excel. The format of these files is documented in the VOSviewer manual. When you download VOSviewer, an example of a map and a network file is included in the ZIP file that you will obtain. However, creating your own map and network files is something which requires an in-depth understanding of VOSviewer. If you have only limited experience with the software, I don't recommend to take this approach.
      If you want to use Scopus data, you need to download data using the CSV export feature in the Scopus web interface. The CSV files obtained in this way can be provided as input in the 'Create Map' wizard in VOSviewer. However, at the moment, there is a bug in the Scopus CSV export, and therefore this approach may not work. Elsevier is working on fixing the problem. An alternative could be to work with Web of Science data.
      Reply
  • Ali H December 29th, 2017 2:06 pm
    Dear Friends
    When I open a CSV from scopus, most time I see error:
    Incorrect number of columns
    It's very time consuming to repair it by finding the incorrect columns. can you help?
    Reply
    • Ludo Waltman December 29th, 2017 2:29 pm
      Unfortunately, there currently is a bug in the CSV export of Scopus. This is causing the problem that you mention. We are in contact about this issue with the Scopus team. They are working on fixing the problem. I hope the problem will be solved soon.
      Reply
      • Kirsty S February 12th, 2018 3:22 pm
        Does anyone have a Scopus file that works that they might be able to share (or at least share the column headers) so that I can work out which columns are required?
        Reply
        • Ludo Waltman February 12th, 2018 3:30 pm
          Please send me an e-mail (waltmanlr@cwts.leidenuniv.nl) and I will try to help you with this.
          Reply
  • Marcela C December 19th, 2017 4:08 pm
    Hi,
    I'm using VOSviewer 1.6.6 for a bibliometric study based on records from Web of Science.
    When performing "bibliographic coupling" on documents, why do I still get results in terms of "total link strength"? Shouldn't I get a different score such as "bib. coupling"?
    Thank you
    Reply
    • Ludo Waltman December 19th, 2017 10:09 pm
      In your case, 'total link strength' can be understood as the total bibliographic coupling strength. VOSviewer currently does not adjust the terminology it uses to the specific type of analysis that is carried out. In future versions of the software, we do plan to adjust the terminology used by the software to the type of analysis.
      Reply
  • dennis December 4th, 2017 11:01 pm
    hello,
    is writing the thesaurus the only way to clean data? because when you have thousands of keywords, writing the thesaurus is really time consuming. Maybe there is another software to assist the cleaning phase? what do you suggest?
    Reply
    • Ludo Waltman December 4th, 2017 11:34 pm
      Yes, this is the only option provided by VOSviewer for cleaning your data. I don’t have specific suggestions for other software tools that you could use for this purpose. However, I do want to mention that in many cases superficial cleaning of keywords may actually be sufficient. As developer of VOSviewer, my recommendation usually is not to focus too strongly on individual keywords appearing in a map, but instead to take a more holistic perspective focusing on the overall patterns emerging from a map. If the latter approach is taken, detailed cleaning of keywords usually is not necessary, and more superficial cleaning is likely to be sufficient. Hence, I often recommend to try to be pragmatic in data cleaning.
      Reply
    • Gilberto Parra January 28th, 2018 9:01 am
      You can try OpenRefine
      Reply
  • Evan Sterling November 30th, 2017 5:25 pm
    The Organization unit option does not appear when I create a map from Scopus data, even though I have double-checked that the CSV files include the Affiliation column, and have tried with multiple data sets. Can you suggest any reasons this might be happening? My export includes all available Scopus fields.
    Reply
    • Ludo Waltman November 30th, 2017 7:30 pm
      The option to create co-authorship maps of organizations based on Scopus data is no longer supported by VOSviewer. This option has been removed in the most recent version of the software (version 1.6.6). The reason is that Scopus (unlike Web of Science) doesn't perform any harmonization of organization names. We therefore felt that Scopus data is not sufficiently clean to create proper co-authorship maps of organizations.
      Reply
  • Dlan November 8th, 2017 1:36 pm
    Hi Ludo,
    When running VOSviewer, I encountered a problem pertaining to being out of memory.
    Number of articles - 35,100
    Numbers of input txt files - 71 (web of science)
    Based on the VOSviewer Manual, I attempted to increase the memory for VOSviewer. However, I could not find the VOSviewer JAR file.
    I downloaded the zipped file of VOSviewer and unzipped it in a different folder. From this folder, I ran the exe file of VOSviewer. In this folder and in my computer, there is no VOSviewer JAR file.
    My computer has 8 GB RAM.
    I would be glad if you could help solve my problem.
    Thank you.
    Reply
    • Nees Jan van Eck November 9th, 2017 2:18 pm
      The VOSviewer JAR file can be obtained using the link 'Download VOSviewer 1.6.6 for other systems' on the Download webpage.
      Reply
  • Daniel October 22nd, 2017 2:42 pm
    Awesome software! Thank you for making it available to all! Is it possible to merge two databases, one extracted from Web of Science and the other from Scopus and have the data analyzed it jointly by VOSviewer?
    Reply
    • Ludo Waltman October 23rd, 2017 10:34 pm
      Please see below the question by Ana on September 2nd, 2015.
      Reply
  • Charis Papaevangelou October 22nd, 2017 12:59 pm
    Hello!
    First off, I'd like to congratulate and thank you for your amazing work!
    I have two quick questions to ask:
    1) Will it be possible in the future to change clusters/items in real-time? For example, while working with one corpus, and you decide that it's actually not that meaningful and want to remove it.
    2) Are other languages going to be supported someday? I'm interested in working with Greek, which is my first language, and VOSviewer does not currently support them, to my understanding.
    Thank you once again :)
    Reply
    • Ludo Waltman October 23rd, 2017 10:32 pm
      Thanks Charis for your suggestions. Although we do not yet have concrete plans for the two points that you mention, we will keep your suggestions in mind for future versions of VOSviewer.
      Reply
  • Pedro October 11th, 2017 2:23 pm
    Topic: Bibliometric data analisys based on keyword occurence.
    Is it right to say that the lines connecting the keywords on my network are a representation / description of how many time those keywords were used simultaneously?
    Could I infer more information from this lines interpretation?
    Cheers and thanks beforehand!
    Reply
    • Ludo Waltman October 11th, 2017 5:56 pm
      Yes, that is correct, the strength of a line (link) indicates the number of documents in which two keywords are used together. The thickness of lines in the visualization is proportional with their strength, although it may be difficult to visually distinguish between lines with different thickness.
      Reply
      • Mihaela October 15th, 2017 5:12 pm
        Regarding the difficulty to distinguish between lines. Is there any way to export these data and import into another program (excel for example) in order to sort by link strength and identify the strongest links?
        Reply
        • Ludo Waltman October 15th, 2017 10:28 pm
          Yes, this can be done by saving a network in a VOSviewer network file. The 'Save' button on the 'File' tab in the action panel of VOSviewer can be used for this purpose. A VOSviewer network file is a simple plain text file that can be imported for instance into MS Excel.
          Reply
  • Isabel Pinho October 2nd, 2017 12:06 pm
    In this article:
    Van Eck, N.J., & Waltman, L. (2017). Citation-based clustering of publications using CitNetExplorer and VOSviewer. Scientometrics
    In pag 1060, fig1-show 22 clusters from CiteNetExplorer
    Next, in pg 1063, fig 3- using VOSviewer to analize those 22 clusters
    How Can I do the same?
    If you please, can you give the tutorial steps to make the visualization in VOSviewer of the 22 clusters that can from CitNet Explorer?
    Reply
    • Ludo Waltman October 3rd, 2017 12:03 am
      Performing an analysis similar to what is reported in this paper is not entirely trivial. It requires an extensive knowledge of VOSviewer and CitNetExplorer and also some data processing skills. As we write on p. 1065 in the paper, “the combined use of the two software tools is somewhat laborious, and preparing the input data for VOSviewer based on the clustering results provided by CitNetExplorer is not entirely straightforward”.
      Basically, you need to take the following steps:
      1. In CitNetExplorer, cluster the publications and export the clustering results. To export the clustering results, choose the option ‘Export groups – Full network’ in the ‘Groups’ menu. Also make sure to save the citation network in a publications and a citations file (using the ‘Save’ button).
      2. Based on the cluster assignments of publications as well as the citation links between publications, it is now possible to construct a citation network of clusters. This requires some data processing skills. Constructing the citation network of clusters for instance can be done using MATLAB, R, or Python.
      3. The citation network constructed in step 2 needs to be saved in a VOSviewer network file. In addition, a VOSviewer map file needs to be created, providing basic information for each of the clusters (e.g., a label and a weight, where the weight can be calculated as the number of publications belonging to the cluster). More information about map and network files is provided in the VOSviewer manual.
      4. In VOSviewer, click ‘Create’, choose ‘Create a map based on a network’, select the map and network files created in step 3, and follow the remaining steps in the ‘Create Map’ wizard.
      I hope the above explanation is helpful, but I understand that some of the steps, especially step 2, may still be quite challenging.
      Reply
  • Minh Nguyen September 4th, 2017 4:23 pm
    Could you elaborate on how the relevance score is calculated in the creation of map based on text data?
    Reply
  • James Qin September 1st, 2017 7:05 pm
    Is it possible to restrict the analysis to a subset of items in VOSviewer published in a specific period? If yes please let me know how to do that. Thanks!
    Reply
    • Ludo Waltman September 2nd, 2017 10:37 am
      This currently is not possible. It is a feature that we hope to add in some future version of VOSviewer.
      Reply
  • Khan jee August 22nd, 2017 9:03 am
    It's a nice endeavor, i appreciate as is very much helpful in research domain.
    Reply
  • Armando Lenin Támara Ayús August 1st, 2017 3:03 pm
    Best regard,
    I am interested in using VOSviemer to do a literature review for my doctoral thesis. I would like to have the manual to maximize the benefits of the software.
    Thank you
    Reply
  • Marcelo Dionisio July 15th, 2017 6:42 pm
    How does it work with a mendeley ris file ? I exported a file with 143 articles but could not find a way to creat a map based on the most cited words or subjects.
    Reply
    • Ludo Waltman July 15th, 2017 10:17 pm
      To create a map based on a RIS file, click the 'Create' button and choose either the second ('Create a map based on bibliographic data') or the third ('Create a map based on text data') option in the first step of the 'Create Map' wizard. In the second step of the wizard, make sure to select the 'RIS' tab.
      Reply
  • Patrick Kang July 12th, 2017 10:01 am
    Hi I'm new with VOSviewer I selected create a map and choosed create a map based on network data and I selected csv file and then the error came up like this "Error while reading VOSviewer network file (line 1): Item without ID."
    How can I fix it? It could be stupid question but I need to solve this problem.
    Thank you.
    Reply
    • Ludo Waltman July 12th, 2017 10:27 am
      It's probably easiest to start working with data downloaded from Web of Science or Scopus rather than with your own VOSviewer network file. In the 'Create Map' wizard, you then need to choose the second or the third option (create a map based on bibliographic data or based on text data) instead of the first option (create a map based on network data).
      Reply
  • Enzo July 8th, 2017 1:52 pm
    Is it possible to create a map based on bibliographic data via the command line?
    I've tried so far with the -map command but it throws an error, whereas there's no problem when opening the file manually.
    (The file I'm reading is created manually as AU - author_1 AU - author_2 ER - )
    Reply
    • Ludo Waltman July 9th, 2017 12:03 am
      Creating a map based on bibliographic data (e.g., data downloaded from Web of Science, Scopus, or PubMed) via the command line is not possible. VOSviewer currently doesn't have any command line parameters to support this. The -map parameter can be used only for creating a map based on a VOSviewer map file.
      Reply
  • agnes June 15th, 2017 3:20 am
    Hi, is there a glossary of terms that go with VOSviewer/ datavisualisation in general? eg "weighted", "normalised weight", "total link strength", etc
    I have found that most software/articles assume this knowledge on behalf of the user/reader
    Reply
    • Ludo Waltman June 15th, 2017 8:08 am
      We don't have such a glossary for VOSviewer. In the coming months, we hope to improve and extend the documentation that is available for VOSviewer users, including a better explanation of the terminology used in the software. If you want to know more about the meaning of specific terms, then please don't hesitate to ask.
      Reply
      • agnes June 19th, 2017 12:02 am
        Thanks for your reply Ludo. Great to hear there will be some updates coming soon. I have read through most of the articles referenced in the manual and not coming from a mathematical background I am having trouble understanding how things such as kernels and total link strength are developed and defined.
        Reply
  • mary June 13th, 2017 11:52 am
    Hi,
    I just downloaded the Vosviewer from this site to visualize the co-citation of authors belong to a university. First, the one that I downloaded does not have Map Tab...the video show this tab...How?
    Second, the file that I got from Web of Science and saved as a plain text...automatically saved in Word with Unicode-F8...so when I create shows ERROR ....Please help me in these two cases.
    Looking forward hearing from you
    Reply
    • Ludo Waltman June 14th, 2017 1:22 am
      The video offers a first introduction into VOSviewer, but it is not entirely up to date anymore. The video was created using an earlier version of the software. This explains why the user interface looks somewhat different from the current version of the software.
      Could you please send me the file that you have downloaded from Web of Science? I will then take a look at it and I will try to give you some advice.
      Reply
      • mary June 14th, 2017 7:07 am
        Hi,
        Thanks for the reply.
        How shall I upload the file???
        Reply
        • Ludo Waltman June 14th, 2017 8:29 am
          Please send the file to me by e-mail. Thanks!
          Reply
    • maryam June 17th, 2017 6:41 am
      Hi,
      I already emailed you Nd attached the file.
      Regards
      Maryam
      Reply
  • Roberta Salgado Gonçalves da Silva June 8th, 2017 3:22 pm
    I have imported a TXT file from Web of Science, but I´d like to know how to import it to VosViewer. I´ve tried TXT and Excel but it didn´t work.
    Thanks
    Reply
    • Ludo Waltman June 8th, 2017 7:32 pm
      Your question is very general and therefore hard to answer. More information is needed: What is the file format of the text file that you have downloaded from Web of Science (plain text, tab-delimited, or something else)? What kind of analysis are you trying to carry out using VOSviewer? Did you use the 'Create Map' wizard, and which steps did you take in the wizard?
      Reply
      • Salgado June 8th, 2017 8:17 pm
        Now I found myself. Thanks
        Tab-delimited
        Create a networking
        Reply
  • Robert June 7th, 2017 4:12 am
    is there a 101 guide on adding more memory to the VOS viewer software in PC and mac?
    Reply
    • Ludo Waltman June 7th, 2017 10:38 am
      The best information we have available on this is provided in Section 4.3 of the VOSviewer manual. When you are using the Windows version of VOSviewer (as opposed to the Mac or JAR version), the software should already be able to access most of the memory available on your system, so in that case there most likely is not much to gain by trying to make more memory available.
      Reply
      • robert June 14th, 2017 2:21 pm
        OK< in the mac (terminal) when i use the jar file, it keeps running (when calculating the relevance scores) and doesn't ever stop?
        Reply
        • Ludo Waltman June 14th, 2017 2:27 pm
          Could you please send me your input file by e-mail? I will then try to take a look at it.
          Reply
  • R Drijvers May 16th, 2017 1:24 pm
    Dear,
    I can't use Web of Science, because I don't have an account. But I can't seem to register a new account. Is there an other program I can use to load the files to VOSviewer?
    Thank you
    Reply
    • R Drijvers May 16th, 2017 1:29 pm
      Never mind!
      Reply
  • Eliane April 17th, 2017 7:51 pm
    I have a keyword map, but I have one doubt: what kind of counting is co-occurrence?
    The occurrences refers to the keywords of the title of the article?
    I chose the options: co-occurences and All keywords.
    Reply
    • Ludo Waltman April 19th, 2017 9:46 am
      This does not refer to keywords in the title (or the abstract) of a publication. Instead it refers to keywords assigned by the authors of a publication (or perhaps by the journal in which the publication has appeared). In the case of Web of Science data, this also includes algorithmically generated keywords, the so-called KeyWords Plus. In the case of PubMed data, MeSH terms are seen as keywords.
      Reply
      • David June 5th, 2017 4:18 pm
        Hi Ludo,
        So is there no way to feed article titles into VOSviewer? Is there a way to "dummy up" an RIS by placing the article titles into keywords fields?
        Thanks,
        David
        Reply
        • Ludo Waltman June 5th, 2017 5:42 pm
          Titles and also abstracts can serve as input for VOSviewer by using the third option ('Create a map based on text data') in the 'Create Map' wizard.
          Reply
  • rodney March 28th, 2017 2:23 pm
    need this
    Reply
  • Devina March 9th, 2017 4:56 pm
    Hello,
    Are there any features for embedding a map visualisation on a webpage? Or would I need to provide a link to the map, where the user opens the map on their own desktop?
    Thank you!
    Devina
    Reply
    • Ludo Waltman March 9th, 2017 5:33 pm
      It is possible to make a map available online using the approach outlined in Section 4.2 of the VOSviewer manual. The map is not really embedded on a webpage (this is a feature that is currently under development), but instead a link is produced that enables users - with just a single mouse click - to download VOSviewer and to open a map .
      Reply
      • Devina March 9th, 2017 5:59 pm
        Thank you for confirming Ludo! I appreciate the swift response.
        Reply
  • Stephen March 8th, 2017 1:40 pm
    error while reading pubmed file' pubmed result 2.text" (line 17): file in invalid.....above this command i was getting using VOS viewer.. how to salve this... I download the data from pubmed...key word search "zika Virus" duration 2011-2016... please give some idea...
    Reply
  • Steph Link February 9th, 2017 11:41 pm
    Hello.
    When downloading data from Scopus, do I have to extract "All available Information" or will Vosviewer also work if I only extract "Citations, abstracts, and references"?
    Thanks
    Steph
    Reply
    • Ludo Waltman February 11th, 2017 8:00 pm
      It seems that downloading only citations, abstracts, and references is sufficient when working with Scopus data in VOSviewer. In general, however, my recommendation is to download as much data as possible. From this point of view, downloading all available information seems the best approach to me.
      Reply
  • Christopher Guy December 27th, 2016 9:01 pm
    I am curious the best way to load data from scopus using a mac. Any suggestions would be helpful.
    Reply
    • Nees Jan van Eck December 28th, 2016 7:56 pm
      In an earlier message that I posted on October 4 (see below), I briefly explained how to download Scopus data that can be used in VOSviewer. The explanation applies to all systems, including Mac.
      Reply
    • PEDRO HENRIQUE December 29th, 2016 3:11 pm
      https://www.youtube.com/watch?v=li6SsJKW5Lw
      Reply
  • Pedro December 20th, 2016 6:51 pm
    WOS data-base; Co-occurence analysis; All keywords.
    Looking for the top related keywords on my database, the software found many similar keywords, where on the end they are the same, for example: "logistic regression"; "logistic regression (lr)"; "logistic-regression"; "logistic-regression model"; "logistic-regression models"; "multiple logistic-regression".
    Is there any possibility to merge those items?
    Is it possible to merge them by hands (after exporting the keywords) and input on the software for further calculations?
    Reply
    • Ludo Waltman December 20th, 2016 7:49 pm
      Yes, VOSviewer provides functionality for merging these keywords. This can be done using a so-called thesaurus file. For more details, please see the VOSviewer manual. Also, when downloading VOSviewer from the Download page on the VOSviewer website, you will obtain a ZIP file that includes an example of a thesaurus file.
      Reply
      • Pedro Lima December 21st, 2016 11:49 am
        Thanks! I will take a look!
        Reply
  • margarida rodrigues December 12th, 2016 11:31 am
    Can you provide a manual please? if it exist in portuguese better
    thank you
    Reply
    • Ludo Waltman December 12th, 2016 11:35 am
      A manual (in English) is available on this page. You have probably overlooked it.
      Reply
  • Gene Major October 14th, 2016 3:40 pm
    Hello,
    I'm new to VOSviewer. I downloaded 1.6.5 for the Mac. I selected create a map based on bibliographic data, upload my WoS text files, but when I get to the Type of analysis screen, the Citation, Bibliographic coupling, and Co-citation options are greyed out...I can't choose them. I can only choose Co-authorship and co-occurance. Is there something I'm doing wrong or are these options not available on the Mac version?
    Reply
    • Ludo Waltman October 14th, 2016 7:21 pm
      This is not a Mac issue, but most likely it has to do with the way in which you have downloaded your data from Web of Science. When downloading data from Web of Science, you need to make sure to select the Web of Science Core Collection (rather than the default ‘All Databases’ option). Also, in the ‘Send to File’ dialog box in Web of Science, you need to make sure that you choose to download all fields rather than just a subset of all fields. To do so, in the ‘Record Content’ drop-down box, you need to select ‘Full Record and Cited References’.
      Reply
      • Gene Major October 14th, 2016 7:54 pm
        Thanks...I thought I had done all that, since thats the way i usually extract data out of WoS. I'll check again, though. Thanks again!
        Reply
      • Gene Major October 21st, 2016 4:29 pm
        Thanks Ludo. The WoS works fine. Now I have a question on Scopus. I export the results as a CSV file. And I tried all 4 options: citation only, citation +abstract, citation+abs. + reference, All the data. When I export into VosViewer (using the Scopus option), I get an error about "incorrect number of columns" for each option I try. Is there a specific set of Scopus fields I should be downloading? Thanks
        Gene
        Reply
  • Ola S October 4th, 2016 1:56 am
    Dear Developers,
    I believe the interface of Scopus has changed recently and there is no way to download data like it was used to be in the past.
    Reply
    • Nees Jan van Eck October 4th, 2016 1:23 pm
      The Scopus interface indeed has changed, but downloading data is still possible in the same way as it was in the past. You need to perform a search in Scopus, select the records that you want to download, and click 'CSV Export' (do not click 'Download'!). Your data will then be downloaded in a CSV file. This file can be opened in VOSviewer.
      Reply
      • Ola S October 5th, 2016 4:52 pm
        Thank you for the prompt response. Apparently a user needs to set in their preferences that they want to download a CSV and say which data goes into it. After these preferences are updated, the CSV download appears as an option.
        I have a second question: is there a way to Use the data from Vosviewer to create a network in Gephi, a network that shows directionality - which journal cites more from the other. E.g. There are two journals: A and B. Articles in journal B very often cite articles from journal A, but A does not cite for B. Is there a way to represent it with arrows? (I know it is somehow represented spatially).
        Reply
        • Nees Jan van Eck October 5th, 2016 10:13 pm
          Unfortunately, VOSviewer completely ignores the directionality in networks, also when saving data in a GML file, which can be used to load the data in Gephi. We plan to take into account directionality in future versions of VOSviewer, but at the moment this is not yet supported.
          Reply
  • jagdish Vyas September 12th, 2016 1:22 pm
    If I want map of data in Excel File (Input) Then How to use vosviewer software
    Reply
    • Ludo Waltman September 12th, 2016 3:39 pm
      Your question is too general. Please first read the book chapter available above, and then please try to formulate a more specific question. For instance, explain the type of data you have and explain what kind of visualization you would like to produce.
      Reply
  • Wagner Pinheiro August 22nd, 2016 3:53 am
    Hello,
    I'd like to know what the difference is between the types of Analysis options "Citation" and "co-citation" . Is the " Citation" like a direct citation?
    Reply
    • Nees Jan van Eck August 22nd, 2016 8:13 am
      Yes, in the case of 'citation', links between items represent direct citation links. For instance, if your items are authors, the strength of the link between two authors X and Y equals the number of citations given by author X to author Y plus the number of citations given by author Y to author X.
      On the other hand, in the case of 'co-citation', links between items represent co-citation links. For instance, if your items are cited references, the strength of the link between two cited references equals the number of publications in which the two cited references both occur.
      Reply
      • Wagner Pinheiro August 22nd, 2016 12:48 pm
        Thnak you Dr. Van Eck !
        Reply
  • Mehmet August 19th, 2016 6:53 pm
    Hi,
    I am using "map based on text data" feature of the tool. It has worked great when I have introduced raw text (abstracts or full text). What I would like to do is getting maps by introducing terms (noun phrases (NPs)) that I extracted from the same textual data with using a different tool. For example, I have been working on publications from alternative medicine and have already obtained nice clusters when relying on VOSviewer NPs. For the same text, I have extracted MeSH terms using an API provided by NHI. Now I would like to employ those MeSH terms in VOSviewer to compare it to my previous results. To this end, I have fabricated sentences like "The term is traditional Traditional Chinese Medicine. The term is obesity. The term is diabetes. " and so on. For each document I have applied this logic and used them in VOSviewer. As a result, I have been offered some term by VOSviewer and I have managed to get the map. However, when I have realized that VOSviewer failed to extract many terms which were quite obvious noun phrases. So does what I have tried make sense? Is there any suggestions?
    I hope I could explain clearly.
    Thanks in advance.
    Kindest regards,
    Mehmet
    Reply
    • Ludo Waltman August 19th, 2016 7:29 pm
      If you know which MeSH terms occur in which of your publications, you can calculate (e.g., using MATLAB, R, or Python script, or using some other software tool) for each pair of MeSH terms the number of publications in which the terms both occur. In other words, you can calculate the co-occurrence matrix of your MeSH terms. My recommendation is to take this approach and to produce a VOSviewer map file and a VOSviewer network file. The format of these files is described in the VOSviewer manual. Also, when you download VOSviewer, examples of a map and a network file are provided. After creating a map and a network file, you can choose the option ‘Create a map based on network data’ in the ‘Create Map’ wizard. You can then provide your map and network files as input to VOSviewer, and VOSviewer will produce a visualization of the co-occurrence network of your MeSH terms.
      I hope this solution is helpful to you. Please feel free to contact me if you experience any difficulties.
      Reply
  • Manuel Castriotta August 9th, 2016 12:15 pm
    Document bibliographic coupling and "counting method" issues.
    Dear all,
    I am conducting an analysis of "document bibliographic coupling" with Vos 1.6.4 and I had a doubt about the "counting method" choice.
    I imagine that the example you propose when you click on (?), in order to explain the "fractional counting", refers to a co-authorship analysis. I is very clear: "if an author co-authors a document with ten other authors, each of the 10 co-authorship links has a weight of 1/10 ".
    However, when i try to translate it to document bibliographic coupling dynamics, I have some troubles in order to understand how "fractional counting" work and if this makes sense.
    Could you please help me by giving an example of the way in which the software "fractionalize" document bibliographic coupling?
    Thanks in advance for any clarification and suggestions.
    Best wishes
    Manuel
    Reply
    • Ludo Waltman August 9th, 2016 5:13 pm
      It is fully understandable that the meaning of fractional counting in the case of bibliographic coupling is not immediately clear to you. I would like to draw your attention to a recent paper in which the distinction made in VOSviewer between full and fractional counting is explained in detail, not only for co-authorship analyses, but also for bibliographic coupling and co-citation analyses. The paper is available in the arXiv and can be found here: http://arxiv.org/abs/1607.02452. Please don't hesitate to post follow-up questions if things are still not entirely clear after reading the paper.
      Reply
  • burcu umut zan August 3rd, 2016 2:56 pm
    Hello, I am trying to learn vosviewer. I took my data set from Wos. I use both of two programs vosviewer and citnetexplorer. I use citnetexplorer for direct citation analyse.
    Here is my problem
    At first I created a map based on bibliographic data in vosviewer, I selected type of analysis as a citation with using source unit analyse. So, I had chance to see the citation numbers of publications.
    Then I used citnet explorer for the same bibliographic data. But when I compare the citation score in two programs I recognized that some citation score of some authors are not consistent with each other.
    For example, there are 40 citations for Leydesdorf in Citnet explorer, but there are 50 citations in vosviewer.
    I could not solve the origin of my problem, where am I doing wrong?
    I will be very hapy to hear your reply.
    Reply
    • Ludo Waltman August 5th, 2016 11:45 am
      This is an excellent question!
      The explanation of the differences you observe between VOSviewer and CitNetExplorer is as follows. VOSviewer shows the total number of times a publication has been cited in Web of Science, while CitNetExplorer shows the number of times a publication has been cited by other publications in your data set. This is the reason why CitNetExplorer systematically shows lower citation counts. Citations received from publications in Web of Science that are not in your data set are not counted in CitNetExplorer, while they are counted in VOSviewer.
      The idea is that in the next version of CitNetExplorer it should be possible to choose between the two ways of counting citations. So users of CitNetExplorer should be able to choose whether they want to see the total number of citations a publication has received in Web of Science or only the citations a publication has received within the data set at hand.
      Reply
  • Leonardo Eljach July 12th, 2016 11:35 pm
    Hello,
    First of all thank you very much for making this software available for all.
    how we can export data from WoS to vosviewer for creating a map of scientific field ?.
    Leonardo
    Reply
  • Ali Abdulhay June 6th, 2016 11:15 am
    Hello,
    When applying "Create a map based on text data" along with WoS abstracts, is it possible to get which UT codes contain extracted terms?
    For example,
    term1 --> UT1,UT2,UT3..
    term2 --> UT1,UT5,UT12
    ...
    Kindest regards,
    Mlee
    Reply
    • Ludo Waltman June 6th, 2016 11:29 am
      In the final step in the ‘Create Map’ wizard, a list of all selected terms is shown, offering the possibility to verify the selection of terms. In this step, you can right-click on the list of terms. This will bring up a context menu in which you can choose the option ‘Export document-term relations’. By choosing this option, you will obtain a text file that on each line contains a relation between a term and a document. The documents have numerical IDs. The document with ID 1 is the first document in your Web of Science file, the document with ID 2 is the second document in your Web of Science file, and so on. The terms also have numerical IDs. The link of these IDs with the actual terms can be obtained by choosing the option ‘Export selected terms’ in the above-mentioned context menu.
      Reply
      • Ali Abdulhay June 6th, 2016 12:21 pm
        It is great!
        For my work it is not only helpful to visualize the network, but also extracting key phrases to use them in other platforms. Especially when dealing with long text such as full texts or introduction section there would be plenty of uninformative terms. By getting phrases by means of co-occurrence filtering more meaningful phrases could be accessed.
        Thank you very much!
        Reply
  • Ali Abdulhay June 2nd, 2016 2:18 pm
    Hello,
    I have used VOSviewer to cluster scientific publications by applying their canonical
    sections such as introduction, conclusion and their citing reference titles to compare
    the results with the ones based on only abstracts. So far I have obtained good results
    especially when using noun phrases (NPs) containing more than one word. To do this, I
    have manually removed those NPs having only one word. However, it took a lot especially
    when dealing with introduction sections. At this point, I have two comments about the
    features of VOSviewer.
    1) It would be nice to have an option allowing user to retain only those terms or NPs
    having more than one word.
    2) As I know, VOSviewer uses only apache's OpenNLP. I guess this choice was made due to
    its speed. I have been using stanfordNLP for a while and I can say that when more complex
    sentences are present it is more successful than OpenNLP to parse them and extract NPs.
    However, it is slow. My suggestion is that it would be great if the user is allowed to
    load his/her NPs. In other words, I have extracted NPs using stanfordNLP in a different
    environment and using them and see the results in VOSviewer would be great.
    Kind regards,
    Mehmet
    Reply
    • Ludo Waltman June 2nd, 2016 5:16 pm
      Thanks a lot for both suggestions. This type of feedback from the VOSviewer user community is always very much appreciated. We keep track of all suggestions made by users of VOSviewer, and we take this into account when determining the priorities for new features to be added to the software.
      Reply
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