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

Comments

Mandatory fields
  • Ayaz Khan May 21st, 2020 2:37 am
    how can we calculate normalized citation and average normalized citation and what is the significance of this?
    Reply
    • Ludo Waltman May 21st, 2020 7:23 pm
      Please see p. 37 in the VOSviewer manual.
      Reply
  • Mia Be May 20th, 2020 8:00 pm
    I have 1,271 articles and when I go to choose the type of analysis only co-authorship and co-occurrence options are possible.
    AND
    When I choose co-occurrence an error message pops out "Insufficient number of keywords. There must be at least three keywords".
    Help please and thx
    Reply
    • Ludo Waltman May 20th, 2020 8:06 pm
      Perhaps there are no or almost no keywords in your data. Could you tell more about the type of data you are working with? What is the data source?
      Reply
  • Kai May 20th, 2020 11:54 am
    My computer environment is: masOS Mojave. My vosviewer has been running without any problems before. Recently, clicking and finishing will cause a flashback. This is the case every time. This crash phenomenon can also be caused by a small amount of data, and java environment everything is normal. What should I do? Please help.
    Reply
    • Ludo Waltman May 20th, 2020 8:03 pm
      Sorry to hear about this problem. You seem to be the first one reporting this issue. I don't have an immediate solution. If others experience the same problem, I would be interested to know.
      Reply
  • James Hill May 19th, 2020 1:59 pm
    Is there a way to open the map file .txt In Excel which would allow editing of the individual outputs. I know when I opened it in Excel it currently puts all the information into a single column is there anyway to separate it out into individual columns?
    Reply
    • Ludo Waltman May 20th, 2020 7:49 pm
      It should be possible to fix this by using the 'Text to Columns' feature in Excel (in the 'Data' menu).
      Reply
      • James Hill May 22nd, 2020 11:26 am
        Thank you so much!!! you saved me many hours of work.
        Reply
  • Boryana Georgieva May 19th, 2020 1:43 pm
    I am missing the .jar file after I download it from vosviewer.com/download for Windows. I need the .jar file to take a network from Rstudio into vosviewer. How can I get the file? Am I doing something wrong?
    Reply
    • Ludo Waltman May 20th, 2020 7:38 pm
      You need to use the link 'Download VOSviewer 1.6.15 for other systems'. This will give you the JAR file.
      Reply
  • Anirudh Badarinath May 15th, 2020 2:12 pm
    Hi!
    Is there a way that I can exclude certain keywords from the co-occurance map (if they're remote and very scantily connected) using the thesaurus file?
    Thanks!
    Reply
    • Ludo Waltman May 15th, 2020 8:13 pm
      Yes, this is possible, simply by leaving the 'replace by' column in the thesaurus file empty.
      Reply
  • Nawaid ALAM May 14th, 2020 9:57 am
    I am a bit confused. With a total of 78 papers, I am conducting Co-citation analysis at the author level. Link Strength between Author A and Author B is 310. Does it mean that Author A and B were co-cited 310 times in the references of included papers? If not, then what should be the interpretation of this link strength value between two authors.
    Thanks in advance
    Reply
    • Ludo Waltman May 14th, 2020 8:02 pm
      Yes, A and B were co-cited 310 times. Why are you confused? Please note that one paper may result in multiple co-citations of A and B. For instance, if A is cited 2 times in a paper and B is cited 3 times in the same paper, this yields 2 x 3 = 6 co-citations of A and B.
      Reply
      • Nawaid ALAM May 14th, 2020 8:59 pm
        Perfect, I am clear now. Thank you
        Reply
  • PJH May 14th, 2020 3:54 am
    Hi
    I am using the temporal overlay on a keyword map and would like to affirm if my understanding is correct.
    I think that for each keyword VOSviewer identifies the distribution of publication years for documents associated with the keyword. Then an algorithm is used to identify when the keyword has been most popular.
    What is the algorithm? For example, do you use the mean, median or another formula to determine the time period and color associated with a keyword?
    Thanks.
    Philip
    Reply
    • Ludo Waltman May 14th, 2020 8:37 am
      We use the mean, so the color of a keyword represents the average publication year of the publications in which the keyword occurs.
      Reply
  • Lorena Rojas May 14th, 2020 1:18 am
    Hi, I love Vosviewer but I want to clean the data that I import first, and the easy tool that I have to do that is Excel ( I don't know how to program :( ), so I want to know if I can somehow import excel data to Vosviewer or If you recommend any free tool for cleaning data. Thanks :)
    Reply
    • Ludo Waltman May 14th, 2020 8:34 am
      What is the source of your data?
      Reply
      • Lorena May 15th, 2020 8:18 pm
        I use different sources, for example, I downloaded bibliographic data of our library OPAC (Sirsy Simphony), to analysis thesis and dissertations to know the most researched topics. Or sometimes I mix information of different databases or sources from grey literature, to do a state of art
        Reply
        • Ludo Waltman May 15th, 2020 8:23 pm
          Thanks for this information. Could you also let me know the file format that you use to provide your data as input to VOSviewer?
          Reply
          • Lorena May 20th, 2020 8:10 pm
            It downloads as .txt delimited by a vertical bar (|)
            Reply
  • Andy Yeung May 12th, 2020 4:37 am
    I would like to ask whether it is possible to check discipline-retained citation ratio. For example, if Paper A belongs to neuroscience (WoS category or Scopus subject area), how many times it is cited by neuroscience papers and non-neuroscience papers?
    Method 1: From WoS / Scopus, I can generate a list of papers citing Paper A, and then check the category / subject area distribution of these citing papers. This should work for a single paper (e.g. Paper A) but do not work for a collection of papers (e.g. if I want to check a collection of Papers A to E). Because a neuroscience paper can contribute to multiple cites, such as cites to all Papers A to E. By this method, 5 citations will show as a single citing paper in the output.
    Can VOSviewer or other solutions help? Would be great to have your recommendations on this. Thank you very much for your time.
    Best regards, Andy
    Reply
    • Ludo Waltman May 12th, 2020 10:11 pm
      It seems to me that this requires API access to a bibliographic database (e.g., Scopus, Dimensions, or Microsoft Academic) combined with some custom programming. I don't think VOSviewer is the right tool for this.
      Reply
  • James Hill May 9th, 2020 10:29 am
    Just wondering if you can help me I am using vosviewer as part of a systematic review around domestic violence. When I separate the citations for a map based on text data into yearly sections 5 years the term partner violence is highly prevalent throughout the data set. With over 807 occurrences out of 2288 citations. However when I add all the citations together and carry out the same analysis the term does not even appear and the number of the individual terms be mentioned separately is not near the 807. Just wondering why this may be occurring as we were planning to do the separate five year analysis and the combined data set analysis? It is difficult to explain why a term can be so highly prevalent throughout the data set was then not appear when you combine them.
    Kind regards James
    Reply
    • Ludo Waltman May 9th, 2020 4:26 pm
      This seems to be caused by the fact that, by default, VOSviewer removes the 40% least relevant terms from the analysis. Relevancy is determined by a text mining algorithm. The algorithm assigns a low relevance to terms that have little value in describing the organization of the literature provided as input to VOSviewer. My guess is that the relevance of the term 'partner violence' is relatively low because the term does not specifically describe one topic within the literature but instead offers a description of the entire body of literature provided as input to VOSviewer. The term 'partner violence' may therefore be a borderline case. In some cases, it may belong to the 60% most relevant terms. In other cases, it may belong to the 40% least relevant terms. I think you should decide yourself whether you want this term to be included in your analysis or not. It is always possible to overrule the default choices in the 'Create Map' wizard to ensure that a particular term is either included in or excluded from the analysis.
      Reply
      • James Hill May 9th, 2020 4:58 pm
        I would first like to say thank you for your reply is a much appreciated your quick response and support with this software.
        It would be important that this term is included . I was thinking along the same lines I tried increasing the threshold to include all terms instead of the standard 60%. The term did appear when I did this but it still had a relatively low occurrence count compared to the individual five year period. I also tried all the other settings in regards to binary counting full counting abstract only et cetera see if it had a similar pattern and it did. Just wondering if you could help me with the command to make sure it counts this time for the combined library. Just that I'm doing this analysis for a research team and it can going to struggle to explain why the term is so prevalent in the five year periods and then when I combine the citations it disappears. Do you know why the occurrence count would be so much lower than the five year periods in both binary and full counting in the combined library compared to the 5 Years Libraries. I would assume when I combine it is not identifying all the occurrences of that term to be important not counting every one of them as it does in the five year period versions. We were planning to make a table which would count the occurrence of the term in each five year period with the idea that it should add up to the same as combined library with all years?
        Reply
        • Ludo Waltman May 9th, 2020 6:33 pm
          When you combine data from multiple time periods, the occurrence counts for the combined data should not be lower than those for the individual time periods. Could you send your files to vosviewer@cwts.leidenuniv.nl? I will then try to reproduce your problem and to offer advice.
          Reply
          • James Hill May 9th, 2020 9:17 pm
            I have sent you the files for you with a bit of a description of the problems if you need any more information or anything about the original endnote file et cetera please not hesitate to ask.
            Kind regards James
            Reply
  • Daniel May 8th, 2020 6:57 pm
    Not directly related to VosViewer software, but is there a way to export bibliometric metadata of more than 500 references at once in WoS?
    Reply
    • Ludo Waltman May 9th, 2020 9:08 am
      I believe the Web of Science web interface doesn't provide a way to export data for more than 500 records. There is a 'Fast 5K' export option, but this option exports only a limited number of data fields.
      Reply
  • nidhi May 4th, 2020 5:18 pm
    How can I get to know about the most productive author by using VOSviewer?
    Reply
    • Ludo Waltman May 4th, 2020 7:24 pm
      VOSviewer is intended for bibliometric network analysis, not for ranking authors. However, when you create a map of a co-authorship network, the size of an author reflects the number of publications of the author, so in this way it is possible to identify the most productive authors.
      Reply
      • Nidhi May 6th, 2020 7:28 am
        Sir

        WoS is showing different most productive author and VOSviewer is showing different. How to justify most productive author in publication.
        Reply
        • Ludo Waltman May 6th, 2020 7:45 am
          I am afraid I cannot help with this very general question. There are multiple ways in which the concept of productivity can be operationalized bibliometrically. You need to choose yourself which approach is most suitable for the purpose of your analysis. The most important thing is to explain why you make a certain choice and to explain the pros and cons of this choice.
          Reply
  • Emily Lee May 1st, 2020 11:07 am
    when i tried to open map, and has finished selecting VOSviewer map file and VOSviewer map file, but it showed error notification,and about 15 seconds later, VOSviewer quit suddenly.
    Reply
    • Ludo Waltman May 2nd, 2020 11:17 pm
      Could you send the map file to vosviewer@cwts.leidenuniv.nl? I will then take a look at your problem. Thanks.
      Reply
  • Anirudh May 1st, 2020 6:29 am
    Hi,
    Thanks for a wonderful tool btw! It's absolutely fantastic.
    I have followed all steps as laid out while exporting from Web of Science. However, when I select 'Create map based on network data' and pick the .txt file (exported from WoS), I get an error message 'incorrect use of quotes'. Any particular reason?
    Can I receive any help?
    Reply
    • Ludo Waltman May 1st, 2020 8:38 am
      When working with Web of Science data, in the first step of the 'Create Map' wizard you should use either the option 'Create a map based on bibliographic data' or the option 'Create a map based on text data'.
      Reply
  • Giuseppe Vito April 22nd, 2020 10:25 am
    Vos Viewer - End Note
    Dear Ludo,
    The answer you gave on April 19th is perfectly correct. However, there are conversations in this blog that explain in detail the procedure for exporting from EndNote. I use EndNote X7 and never find any problem.
    Greetings
    Reply
  • Ahmed Rashed April 22nd, 2020 3:17 am
    OK I'm sorry can u please briefly explain if I have an end note library how i can get the essential data and how to export it from end note what extension and how to import it to VOS viewer to get the authorship map since I'm having a serious difficulty figuring this out
    Reply
    • Ludo Waltman April 22nd, 2020 8:27 am
      I hope there are EndNote users on this forum that are able to provide such an explanation. Unfortunately, since I am not an EndNote user myself, I am unable to offer an explanation.
      Reply
  • Rafael Oliveira April 19th, 2020 9:03 pm
    Dear Ludo,
    I am very enthusiastic about your software tools. And I hope that you do not mind my asking three related questions regarding their differences.
    - Why would VOSviewer and CitNetExplorer yield different cluster solutions for a citation analysis (given the same dataset, the same resolution and optimization parameters and without including non-matching cited references)?
    - Are there differences between the clustering techniques employed by VOSviewer and CitNetExplorer ?
    - Does the former employ the Leiden Algorithm?
    Thank you in advance
    Rafael
    Reply
    • Ludo Waltman April 20th, 2020 11:59 pm
      VOSviewer and CitNetExplorer indeed use the same clustering technique. However, VOSviewer uses a more recent version of the optimization algorithm. VOSviewer uses a variant of the Leiden algorithm, while CitNetExplorer uses an older algorithm. In practice, this shouldn't make a big difference. To obtain similar clustering solutions in the two software tools, it is important to use the 'Fractionalization' normalization method in VOSviewer (see the 'Analysis' tab). Importantly, the resolution values in the two tools do not have the same scale, so a resolution of, say, 0.5 in VOSviewer is not the same as a resolution of 0.5 in CitNetExplorer.
      Reply
  • Rhonda Buskell April 19th, 2020 5:54 am
    Hi, and thank you very much for this software and your time to give any advice. How is lockdown for you in the Netherlands? it seems to be working for us here in Australia at present.
    I'm just using VOSViewer for the first time, and trying to import my bibliographic data from my endnote library. I'm on a Mac, and my EN file names end in .enlx or .enl or .enlp . I've tried all, and either I'm told the file is empty (which I know it is not) or there is an error and, like the previous poster, 'can't find author(%A) or keyword (%K) field'. Can you advise me, please? Thanks, Rhonda
    Reply
    • Ludo Waltman April 19th, 2020 8:14 am
      Different versions of EndNote seems to use different file formats. VOSviewer supports only the ENW file format. I am afraid other EndNote file formats are not supported by VOSviewer. Perhaps you could use the RIS file format as an alternative?
      Reply
      • Rhonda Buskell April 19th, 2020 11:01 am
        Thank you, Ludo, I'll give that a try.
        Rhonda
        Reply
  • Ahmed Rashed April 18th, 2020 6:12 am
    hey, and thanks for such a great software
    I'm trying to conduct a co-authorship map, i have files from endnote since i used 2 different data base web of science and science direct, i export the data to txt type then i open the data in note pad and changed the extension to all files and enw extension went to VOS and i was trying the bibliographic data then data from end note then i had this error stating error while reading end note file : can't find author (%A) or keyword (%K) field
    can you please tell what I'm messing here
    thanks in advance
    Reply
    • Ludo Waltman April 19th, 2020 12:13 am
      Your question is not entirely clear to me. I don't understand why you have manually changed the extension of your file to ENW. The error message indicates that your file is not a valid ENW file. To obtain a valid ENW file, the file should be exported directly from EndNote without making any further manual changes to the file.
      Reply
  • shiza shamin April 13th, 2020 12:10 pm
    Dear Ludo Waltman,
    I just make choice of co-authorship and authors,but all other options are locked.i am using scopus data in .csv file.Can you help me to resolve this problem?
    Thanks in advance!
    Reply
    • Ludo Waltman April 13th, 2020 5:59 pm
      When exporting data from Scopus, you need to make sure to include all available information, in particular information on references. This will enable you to create other types of maps in VOSviewer, in addition to co-authorship maps.
      Reply
  • PJH April 9th, 2020 10:01 am
    Ludo
    Quick question. When conducting journal co-citation analysis is it more correct to refer to the results as "citations" or "co-citations"? For example,
    a. "The Journal of Educational Psychology accrued 2,325 co-citations in the reference lists of the review documents." Or
    b. "The Journal of Educational Psychology accrued 2,325 citations in the reference lists of the review documents." or
    c. both are correct
    Thanks.
    Philip
    Reply
    • Ludo Waltman April 9th, 2020 10:24 am
      VOSviewer in fact provides both statistics. They are available in the 'Weights' drop-down menu. 'Total link strength' is the total number of co-citations of a journal. 'Citations' is the number of citations of a journal.
      Reply
      • PJH April 9th, 2020 10:37 am
        Got it, thanks.
        Philip
        Reply
  • Giuseppe Vito April 9th, 2020 9:27 am
    VosViever EndNote
    Some time ago a user - whom I no longer find in this conversation - suggested the following procedure:
    from EndNote export txt file in "EndNote export" format
    Open the txt file with notepad, save it as "all files" with the extension .enw.
    Done.
    This overcomes, among other things, the problem of combining references from Scopus and Web of Science although limited to Coauthorship and Keywords co-occurrence.
    Hi everyone and congratulations again to Ludo and Nees Jan for the great software.
    Reply
  • LUIZ Martins April 8th, 2020 5:36 pm
    Hi,
    First I would like to thank you for making the software available.
    I have a problem, I have installed and re-installed several times but I cannot make the choice of "Analysis Type" because it is only locked for "Co-authorship" analysis, not allowing changes to the other analysis topics.
    If you can help me I will be immensely grateful.
    Att.
    L. Martins
    Reply
    • Ludo Waltman April 9th, 2020 9:31 am
      Could you let me know which data source you are using?
      Reply
  • Paraskevas April 6th, 2020 11:10 am
    Hi, is it possible to embed somehow the interactive map to my website so I can show the network of the keywords of my publications?
    Or do I need always to provide a link of the map and through that someone can check it on the VOSviewer software? I saw section 5.2 on the manual but I couldn't also understand how to make the map file online. Can you provide a different example please?
    Thank you for the amazing software!
    Reply
    • Ludo Waltman April 7th, 2020 12:15 am
      It is best to follow the instructions provided in Section 5.2 in the VOSviewer manual. You need to take care yourself of making your map file available online. I am afraid we cannot help with this. Perhaps you could ask for help from a local ICT expert.
      Reply
  • Lina April 3rd, 2020 9:32 pm
    Dear Ludo Waltman,
    I'm having trouble doing bibliographic coupling analysis. It only allows me the co-authorship and co-occurance tab as the type of analysis in the creating map tab, all of the data files I draw from the web of science. I'd be glad if you help. Thanks.
    Reply
    • Ludo Waltman April 3rd, 2020 11:31 pm
      When exporting data from Web of Science, make sure to choose the option 'Full Record and Cited References'. This should solve your problem.
      Reply
  • Philip April 1st, 2020 11:20 pm
    Is this an accurate description of 'total link strength'?
    ‘Total link strength’ measures the number and breadth of ‘links’ of one journal with other journals. For example, a journal with given number of co-citations could be frequently co-cited with either a smaller or larger number of other journals. This implies that a journal with higher total link strength has been co-cited with a larger number of other journals.
    Thanks.
    Reply
    • Ludo Waltman April 2nd, 2020 12:01 am
      I think your description is not sufficiently clear. This would be my suggestion: The strength of a link between two journals A and B equals the number of co-citations of publications in journal A and publications in journal B. The total link strengh of journal A equals the sum of the strength of the links between journal A and all other journals. Hence, journal A may have a high total link strength either if it has strong links with a limited number of other journals or if it has weak links with a large number of other journals.
      Reply
      • Philip April 2nd, 2020 12:06 am
        Ludo
        Thanks for the quick response. I'm not surprised that it was not clear! That's why I checked.
        I will use your description with attribution in my future publications.
        Thanks again and stay safe!
        Philip
        Reply
  • Lucas Carvalho March 27th, 2020 10:25 pm
    Dear Ludo,
    I would like to know if there is a possibility to prevent nodes or labels from overlapping in the network view. Is it possible to make all labels apparent in VosViewer?
    Thank you very much for your attention,
    Lucas Carvalho
    Reply
    • Ludo Waltman March 28th, 2020 6:49 pm
      There is no easy solution, but there are a few options:
      1. You could change the values of the attraction and repulsion parameters on the 'Analysis' tab and you could then rerun VOSviewer's layout algorithm. Some parameter values will probably result in less overlap of labels than others.
      2. You could change some of the settings in the options panel, for instance the 'Size' slider or the maximum label length, or you could choose to show labels in frames.
      3. You could save your map in a VOSviewer map file and you could then manually edit this file in a spreadsheet program such as MS Excel. By changing the values in the x and y columns, you can change the location of items in your map.
      Reply
  • James Hill March 10th, 2020 10:20 am
    Just wondering if there's any way to increase the maximum virtual memory? I have been trying to create a map of 51,000 citations and it crashes out indicating that it run out of virtual memory. I've manually given Java 32 GB which should be plenty enough from what I can see within task manager of what It usually crashes out at around about 1 GB to 1.5. I'm assuming the restriction is within the software. The other option which I was wondering if possible was to merge smaller maps together.
    Reply
    • Kebede March 10th, 2020 11:36 pm
      The same thing happened to me. And then I thought this software is useless and I need to look at somewhere less.
      Reply
      • Ludo Waltman March 11th, 2020 7:31 am
        There are no strict limits on the size of the networks that VOSviewer is able to visualize. In practice, however, visualizing networks consisting of more than 5000 or 10000 items becomes difficult in VOSviewer. In general, I recommend against having more than 5000 items in your network. If you want to visualize a really large network, you need to use other software tools, such as Gephi.
        Reply
  • saba March 9th, 2020 7:22 am
    hi. could you please explain to me how to use endnote data in the VOS viewer?
    Reply
  • Lucas March 3rd, 2020 1:49 am
    Dear Ludo,
    First of all, I would like to thank you for the opportunity to ask questions through a direct channel. I am very interested in exploring Wikidata from VosViewer. However, I have been having difficulty finding the DOI of Wikidata articles. How should I proceed?
    Thank you so much in advance.
    All the best,
    Lucas
    Reply
    • Ludo Waltman March 3rd, 2020 7:43 pm
      I am afraid I cannot help with this. Working with Wikidata in VOSviewer requires you to have DOIs of the documents you are interested in. You need to find a way to obtain these DOIs. I cannot offer much advice on this. Instead of Wikidata, you could consider using Crossref or Microsoft Academic. These data sources can be used in more flexible ways in VOSviewer by specifying your own search queries. You don't need to have DOIs for using these data sources.
      Reply
      • Lucas March 5th, 2020 12:41 pm
        Thank you very much, Ludo. I will try the Microsoft Academic.
        All the best,
        Lucas
        Reply
  • Jinhan March 2nd, 2020 4:56 pm
    Hi, please, anyone can help me, how to create a map with Endnote file? How can I prepare Endnote file? Is there any instructions with details? I have a small number of articles in an Endnote group to be analyzed. But the file type confused me. Thanks a looot!
    Reply
  • Andy Yeung March 2nd, 2020 4:17 am
    I just wonder if VOSviewer can allow users to input additional numerical data in an extra column in the data file, e.g. Altmetric score, or score showing the location in a spectrum of basic science-applied research, etc. These data are not export-able or available in Web of Science or Scopus, but are informative.
    Reply
    • Ludo Waltman March 2nd, 2020 7:37 am
      Could you let me know the main data source you are working with (e.g., Web of Science, Scopus, Dimensions, etc.) and the type of map you would like to create (e.g., co-authorship map, citation-based map, keyword/term co-occurrence map)? I may then be able to offer further advice.
      Reply
      • Andy Yeung March 2nd, 2020 11:50 pm
        I usually work with Web of Science data, and create term map and keyword co-occurrence map. The color can represent avg publication year, avg citation count, or norm. citation count. But I want to visualize custom data such as Altmetric score, which is not in the WOS data file but have to add in manually.
        Reply
        • Ludo Waltman March 5th, 2020 8:20 pm
          In the case of a term co-occurrence map, you could create a so-called corpus file containing the titles and abstracts of the publications in your Web of Science file (one title/abstract pair on each line). You could then also create a so-called scores file. On each line in the scores file you can provide a custom score (e.g., Altmetric score). The lines in the scores file should match with the lines in the corpus file. So the first score in the scores file corresponds with the first publication in the corpus file, the second score corresponds with the second publication, and so on. See the VOSviewer manual for more information about corpus and scores files.
          Reply
  • Philip February 26th, 2020 4:33 am
    I have a database consisting of 1,529 articles published in a single journal. When I ran journal co-citation analysis, it showed two journals with more than 1,529 citations. Is this due to those journals having multiple 'co-citations' in some of the documents?
    Thanks.
    Philip
    Reply
    • Ludo Waltman February 26th, 2020 8:17 am
      An article may include multiple references to the same journal. This is why the number of citations of a journal may be greater than 1529.
      Reply
  • Ardita Dorti February 22nd, 2020 2:24 pm
    Dear LudoI am working on constructing a co-occurrence network of keywords. During "Create map Wizard" I have chosen these options:1. Create a map based on bibliometric data2. Read data from bibliometric database files3. Type of analysis: co-occurrence; Unit of analysis: All keywords and Counting method: Full CountingI am trying to understand the difference between Full Counting and Fractional Counting methods in my case. I read on VOSviewer manual: Occurrences. When working with keywords, the Occurrences attributeindicates the number of documents in which a keyword occurs. When working withterms, the definition of the Occurrences attribute depends on the countingmethod that is chosen in the Create Map wizard. In the case of binary counting,the Occurrences attribute indicates the number of documents in which a termoccurs at least once. In the case of full counting, the Occurrences attributeindicates the total number of occurrences of a term in all documents. The difference between counting methods in case of co-occurrence network of terms is clearly explained. 
    Furthermore I read: "Constructing bibliometric networks: A comparison betweenfull and fractional counting" by Antonio Perianes-Rodrigueza, Ludo Waltmanb, Nees Jan van Eckb. In this article there are given examples only for co-authorship, bibliographic coupling, and co-citation networks. Please can you help me understand the difference between full and fractional counting methods in co-occurrence networks of keywords?Note : I use VOSviewer version 1.6.13
    Thank you in advance
    Reply
    • Ludo Waltman February 23rd, 2020 7:44 pm
      The best explanation I have available is the one provided in the paper by Perianes-Rodriguez and colleagues. This paper doesn't focus specifically on co-occurrence networks. However, co-occurrence networks are treated in a way that is fully analogous to the way in which for instance co-authorship networks are treated (since a co-authorship network can in fact be seen as a special case of a co-occurrence network).
      The bottom line is that in general I recommend to use full counting, which has the advantage of being easy to understand. Fractional counting should be used only in special cases and only if you feel you have a proper understanding of the difference between full and fractional counting.
      Reply
  • Pedro February 18th, 2020 1:10 pm
    Dear Ludo,
    We are constructing a co-citation map with the most cited journals regarding a determined subject. When we construct this map, there are two different clusters with many journals. We are trying to understand how works the journals' classification into these two clusters. Is it based on the link strength among the journals? Citations among them?
    Thank you in advance.
    Reply
    • Ludo Waltman February 18th, 2020 11:42 pm
      The clustering is based on the links between the journals in your co-citation network. The larger the number of co-citation links between two journals, the more likely the journals are to be assigned to the same cluster.
      Reply
  • Amir Houshmand February 18th, 2020 6:00 am
    Dear Sir/Madam
    I am trying to increase memory available to VOSViewer in the command line by using the cammand "java –Xmx4000m -jar VOSviewer.jar", but it says: "Error: Unable to access jarfile VOSviewer.jar". Could you please help me to solve the problem?
    Thanks
    Reply
    • Ludo Waltman February 19th, 2020 11:32 am
      When you are in the command line, you need to go to the folder in which the file VOSviewer.jar is located. Otherwise the command won't work.
      Reply
      • Tea Mijac April 1st, 2020 8:32 pm
        Dear Sir/Madam,
        i can't download .jar file. Can you tell me were can i find it?
        Reply
        • Ludo Waltman April 2nd, 2020 12:05 am
          You need to use the link 'Download VOSviewer 1.6.15 for other systems' at www.vosviewer.com/download.
          Reply
  • John February 15th, 2020 6:46 pm
    Dear Sir/Madam,
    I am trying to use the Vosviewer software for Bibliometric analysis, but each time I get a pop message that the excel file from scopus have some wrong quotes. What should I do?
    Reply
    • Ludo Waltman February 16th, 2020 8:49 am
      Data can be exported from Scopus in a CSV file. It is important not to open and save Scopus CSV files in Excel. This often causes problems. You need to download Scopus CSV files without opening them in Excel. I expect that this will solve your problem. If it doesn't, then please send your file to vosviewer@cwts.leidenuniv.nl. I will then try to take a closer look at your problem.
      Reply
      • John February 18th, 2020 3:08 pm
        Hello Ludo,
        Thank you, I tried it and it worked.
        John
        Reply
  • Antonio February 11th, 2020 8:29 pm
    Dear Ludo,
    Thanks again for providing us this powerful tool.
    I’m facing a problem with the bibliographic coupling analysis. When I try to model a network of bibliographic coupling generated by 6000 documents, VOSViewer pop ups an error message: “The number of clusters is too large. Choose a lower value for the resolution parameter”. I have already altered the resolution parameter to lower values (e.g. 0.1 or 0.001) but the same problem occurred. I also changed the minimum cluster size (e.g. 1000), without success.
    When I model the network selecting only the giant component, this problem doesn’t appear. But for me is very important to generate a network including the unconnected items.
    Thank you so much in advance.
    All the best,
    Antonio.
    Reply
    • Ludo Waltman February 14th, 2020 11:03 pm
      My suggestion is to set the minimum cluster size to a value of, for instance, 10 and to uncheck the 'Merge small clusters' checkbox. I think this will solve your problem.
      Reply
  • Diana Gonzalez February 8th, 2020 10:21 pm
    Hello,
    Thank you for developing this very useful tool!
    I'm conducting some analysis of data from Scopus (.csv format) and I'm getting the below error when loading multple files. Could you please advise on how can I resolve it?
    Error while reading file 'scopus.csv': IOException reading next record: java.io.IOException: (line 198) invalid char between encapsulated token and delimiter.
    Thanks for your answer
    Diana
    Reply
    • Ludo Waltman February 9th, 2020 7:05 am
      Could you send your files to vosviewer@cwts.leidenuniv.nl? I will then try to take a look at your problem.
      Reply
      • Diana Gonzalez February 12th, 2020 11:48 pm
        Hi Ludo. Thank you for your support. I had a look at the line 198 and they were extra quotes in one of the sentence besides the delimiter which caused the problem. I removed them and it is resolved.
        Reply
  • Ahmad February 3rd, 2020 4:58 am
    Dear Ludo,
    Greeting for Australia. Thanks for developing this software and maintaining this page. I have a question about the termhood. I just wonder if the item relevance scores can be used as termhood value? or should I separately calculate the termhood score using, say, C-value?
    thanks
    Reply
    • Ludo Waltman February 3rd, 2020 7:54 am
      Could you give some further information? What do you mean by termhood, and why do you feel you need a termhood value?
      Reply
      • Ahmad February 3rd, 2020 1:08 pm
        On page 583 in your below research the termhood is defined as the degree to which a semantic unit represents a domain-specific concept. Different statistical approaches are suggested to measure the unithood and termhood of phrases. For my research I tried to use the NC-value (Frantzi, Ananiadou, & Mima, 2000) to measure termhood but I found its calculation difficult. On the other hand, VOSviewer calculates relevance score for each item (term). The manual says (p 35): ‘Terms with a high relevance score tend to represent specific topics covered by the text data, while terms with a low relevance score tend to be of a general nature and tend not to be representative of any specific topic.’ Therefore, I was thinking if it is possible to use relevance score instead of NC values.
        van Eck, N., Waltman, L., Noyons, E., & Buter, R. (2010). Automatic term identification for bibliometric mapping. Scientometrics, 82(3), 581-596.
        Frantzi, K., Ananiadou, S., & Mima, H. (2000). Automatic recognition of multi-word terms:. the c-value/nc-value method. International journal on digital libraries, 3(2), 115-130.
        Reply
        • Ludo Waltman February 8th, 2020 3:07 pm
          Thanks for clarifying your question. Relevance scores in VOSviewer indeed can be seen as a kind of termhood measures, but VOSviewer doesn't make use of the methods discussed in the paper by Van Eck et al. (2010). Unfortunately, we don't have a paper in which the algorithm used by VOSviewer for calculating relevance scores is documented.
          Reply
          • Ahmad February 11th, 2020 6:10 pm
            Many thanks Ludo
            Reply
  • yare January 30th, 2020 5:41 pm
    Hello,
    First of all, thank you for the program. While analyzing the most cited journals, I encountered the no title captured status. Is there anything I can do?
    Reply
  • Sophie Korth January 30th, 2020 11:12 am
    Hello,
    I've only just started using this tool but I enjoy it already, thanks for the great work!
    I'm trying to build a network using data from both WOS and SSRN. Is there any way to incorporate data from the SSRN database into the WOS format?
    Thanks for your answer!
    Sophie Korth
    Reply
    • Ludo Waltman January 30th, 2020 4:03 pm
      I am afraid that VOSviewer doesn't provide any support for combining data from SSRN and Web of Science.
      Reply
  • Arun Saxena January 23rd, 2020 6:46 am
    Hello
    Seasons greetings for 2020.
    I am facing a problem and hoping you have a solution for this.
    1. VOSViewer produces totally different coauthor network with and without the "Reduce first names of authors to initials". Is this a bug?
    2. The feature in (1) above is reducing names to single initial so introducing error in the network. For example, it takes Li, Y, Li, YL, Li, YH as one name - Li, Y.
    Look forward to your help with this
    Thx
    Arun Saxena
    Reply
    • Ludo Waltman January 23rd, 2020 8:22 am
      No, this is not a bug. You probably have many authors in your data set that have different first names but the same initials. This would explain why the results obtained using initials are so different from the results obtained using full first names. I recommend to use full first names, unless data on first names is missing for a large share of the authors in your data set.
      Reply
      • Arun Saxena January 25th, 2020 8:29 am
        Not really. For example, if the names in my data-set are John AA (1 document), John AB (2 documents), John AC (3 documents) - it combines the results of the three and shows a bubble titled John A with 6 documents. It appears the VOSViewer drops the second initial when computing.
        Reply
        • Ludo Waltman January 25th, 2020 5:07 pm
          Which data source are you using?
          Reply
          • Arun Saxena January 27th, 2020 6:53 am
            I am using Web of Science database downloaded in plain text form.
            Reply
            • Ludo Waltman January 27th, 2020 8:50 am
              Could you send your Web of Science file to vosviewer@cwts.leidenuniv.nl? I will then take a closer look at your problem.
              Reply
              • Ludo Waltman January 27th, 2020 10:43 am
                Thanks for sending me your file. I have looked at it. The problem is that for older publications Web of Science writes the initials of authors without periods, so for instance ‘Yang, BJ’ instead of ‘Yang, B.J.’. Without the periods, VOSviewer is unable to distinguish between an author for which the full first name is reported and an author for which multiple initials are reported. VOSviewer assumes that the full first name is reported and then reduces this name to an initial. Sometimes the assumption made by VOSviewer is incorrect. Instead of the full first name of an author, the initials of the author are reported. VOSviewer then incorrectly removes all initials except for the first one. I am afraid there is no easy way to solve this problem. It is due to ambiguity in author names in Web of Science. Fortunately, this problem seems to be specific to older publications in Web of Science. For more recent publications, Web of Science seems to consistently write initials with periods. VOSviewer will then be able to correctly distinguish between first names and initials.
                Reply
  • Karin Klieber January 20th, 2020 3:42 pm
    Hello,
    thank you for developing VOSviewer. I really enjoy using it. One question: Is it possible to show the names of all nodes in the screenshort? Can I somehow force the program to print all the names in the visualization?
    If not, is it possible to tell the program which names to show in the screenshot? This would be very helpful.
    Thank you and best regards!
    Reply
    • Ludo Waltman January 20th, 2020 6:25 pm
      I am afraid there is no easy solution. By changing the attraction and repulsion parameters of the layout technique, you may obtain a layout in which there is less overlap of labels. Other possibilities are to reduce the size of the items using the 'Scale' slider in the options panel or to decrease the maximum length of the labels.
      There is no possibility to tell VOSviewer which labels should be shown and which ones do not need to be shown. Labels of items with a higher weight always have priority over labels of items with a lower weight.
      Reply
  • Philip January 19th, 2020 12:09 am
    Ludo:
    I have an author co-citation map in the domain of problem-based learning that is comprised of 99 authors or a specific period of time (i.e., not the entire period of the review). In two of the three clusters, all of the scholars represented on the map are associated with 'medical education'. Of course, there were also scholars working on the design of PBL curricula in nursing, dental and engineering and management education as well. But they are not shown on the map since they did not meet the citation threshold.
    I wish to name the schools of thought and am curious whether you think it is more accurate, for example, to call a school "Design of PBL Curriculum" or "Design of PBL Curriculum in Medical Education"?
    Thanks.
    Reply
    • Ludo Waltman January 19th, 2020 8:56 am
      Since I have no expertise in PBL research, I am not sure if I am in the position to answer your question. Based on your explanation, however, it seems to me that 'Design of PBL Curriculum in Medical Education' would be an appropriate label.
      Reply
  • Abhishek Prasad January 15th, 2020 6:34 am
    I just started using VOSviewer and find it an amazing tool for bibligraphic network visualisation. But, when I make coauthorship network for the countries, the labels all begin with small letter. Can you please tell me how to make the Labels start with a capital letter.
    Thanks.
    Reply
    • Ludo Waltman January 15th, 2020 7:54 am
      You need to save your map in a VOSviewer map file. This is a plain text file that can be edited using a spreadsheet program such as MS Excel. Using such a program, you can convert the first letter of the label of each country from lower case to upper case. When you then reopen your map in VOSviewer, the labels will be presented in the desired way.
      Reply
      • Abhishek Prasad January 15th, 2020 9:56 am
        Hey Ludo!!!
        Thanks for the answer. I did what you suggested. While the labels are as I wanted, i am not getting the curved lines in the network anymore. Can it be solved, or do I only get this kind of map from the VOSviewer map file, where there are nodes, but edges are not shown?
        Reply
        • Ludo Waltman January 15th, 2020 3:12 pm
          To maintain the lines (i.e., the edges), you also need to save a VOSviewer network file. The map and network file together contain all data about a map.
          Reply
  • Andréia Anschau January 14th, 2020 10:55 pm
    I would like to use "corpus files" and "scores files" to create maps relating journal names and their impact factors. In “corpus files” I entered the names of the journals and in “scores files” I entered the respective impact factor. However,by generating the map, the full name of the journal does not appear, only the terms of the names. I tried to use “thesaurus file”, but I couldn't solve the problem either. Could you support me to be able to generate a map with the full name of the journals? The rest (legend according to impact factor) and circle size are correct.
    Reply
    • Ludo Waltman January 15th, 2020 12:05 am
      Corpus files are intended to be used for creating term co-occurrence maps. They cannot be used for creating maps of journals. I wonder how you would like your journals to be mapped. For instance, do you want them to be mapped based on citation links, or do you have in mind something else?
      Reply
      • Andréia Anschau January 16th, 2020 1:00 pm
        Good morning, I would like to create 1 map relating the occurrences of the names of the newspapers on my list with their impact factors (JCR). Is there a way to do this in VOSviewer? Another question: I have a list of publications with their citation numbers and another score, but I have questions about how to organize the data for the journal_map.txt file. For example, I don't know how to set the values of "x", "y" and "cluster". In "url" can you put the DOI link?
        Reply
        • Ludo Waltman January 16th, 2020 11:34 pm
          I don't fully understand your questions. Please keep in mind that VOSviewer is a software tool for network visualization. Hence, you need to have network data. In your case, I'm not sure whether you have such data. Perhaps you could clarify this?
          Reply
  • Monalisha Pattnaik January 14th, 2020 5:31 am
    Please give step by step procedure to draw network diagram of co-occurrence using Dimension database.
    Thanks and Regards,
    Reply
  • Monalisha Pattnaik January 14th, 2020 4:20 am
    Please answer about my query. I am not getting the Web of science database.
    Reply
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