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

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  • 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
  • Jose Luis January 13th, 2020 5:52 pm
    I am fascinated with the VOSviewer. I am finishing a paper using it but would like to give access to the map or make the map available online. I have seen the publication on Analytical Chemistry: Bibliometric Mapping: Eight Decades of Analytical Chemistry, WithSpecial Focus on the Use of Mass Spectrometry and the supplementary information provided, as well as read the VOSviewer Manual, but cannot figure it out on how to make it.
    I will appreciate your assistance.
    Reply
    • Ludo Waltman January 13th, 2020 9:02 pm
      The required information is provided in Section 5.2 in the VOSviewer manual. Using this information, VOSviewer can be started from the web and a map can automatically be opened.
      By the way, a truly web-based version of VOSviewer is currently under development and will hopefully be released in the coming months.
      Reply
      • Jose Luis January 14th, 2020 3:59 pm
        Thank you very much Ludo for your answer. I guess I will need to find out how to find a site where to upload the txt files online. I have been trying the domain www.example.org and .com, without luck.
        Look forward for the web-based version.
        Reply
  • Monalisha Pattnaik January 13th, 2020 4:43 am
    I can not access web of science database. Please inform me the way to access this database.
    Thanks.
    Dr. Monalisha Pattnaik, India
    Reply
    • Ludo Waltman January 13th, 2020 7:16 am
      Web of Science can be accessed at www.webofscience.com, but you need to have a subscription. If you don't have a subscription, my recommendation is to use a database that is freely accessible, such as Dimensions (www.dimensions.ai).
      Reply
  • Tal Levi January 12th, 2020 1:49 pm
    Hello!
    What exactly is the formula used in order to calculate item density?
    i can see from density colors txt files that the output for each point is a value between 1 and 0, but how is that calculated?
    thank you very much in advance!
    Reply
    • Ludo Waltman January 12th, 2020 2:35 pm
      This is documented in the following paper: https://doi.org/10.1007/s11192-009-0146-3.
      Reply
  • Monalisha Pattnaik January 12th, 2020 12:36 pm
    please send me step by step procedure to draw the density map using web of science database from network.
    Reply
  • Carlos López-Vázquez January 7th, 2020 7:06 pm
    Thank you for sharing your work. I have a very, very basic question: How to enlarge the font size of the software? I have a high density screen so everything looks tiny.
    I am running the Windows version, but if necessary I might use Ubuntu as well.
    Regards
    Carlos
    Reply
    • Ludo Waltman January 11th, 2020 7:29 pm
      This problem occurs when VOSviewer is used on computer screens with a very high resolution. Unfortunately, in the short term we don't expect to be able to solve this problem. The problem is caused by the user interface library that is used by VOSviewer, and we therefore cannot solve the problem ourselves. As a workaround, my suggestion is to lower the resolution of your screen in your operating system.
      Sorry for not being able to offer a more useful solution.
      Reply
      • Carlos López-Vázquez January 11th, 2020 8:37 pm
        Thank you for yor quick reply. I will look for a workaround.
        Regards
        Carlos
        Reply
  • Lurdes January 4th, 2020 1:04 am
    Dear Ludo,
    Can I perform a valid co-occurrence (type of analysis) of the author keywords (unit of analysis) with only 206 articles?
    Thank you
    Reply
    • Ludo Waltman January 5th, 2020 12:40 pm
      Good question. For me, validity is not a property of the analysis but of the interpretations that are made based on the analysis. I think it is better to rephrase your question in terms of usefulness rather than validity. For term co-occurrence or keyword co-occurrence analyses, I usually suggest to have at least 500 documents. Co-occurrence analyses have clearly proven useful in situations in which there are at least 500 documents. For smaller numbers of documents, the usefulness of co-occurrence analyses tends to be more limited, although the analyses may still yield useful insights. As already mentioned, validity depends on the interpretations made based on your analysis. I therefore cannot make general statements about validity.
      Reply
  • Lena January 3rd, 2020 11:19 am
    Hello,
    I have a question about the citation of authors.
    For example I have 625 citations, 208 total link strength and 135 links. So the focal author has citation links with 135 other authors. With some authors, the focal author has more than one citation link. This is reflected by the total link strength of 208. In total, the focal author has 208 citation links with the 135 authors with which it has citation links, right? But what do the 625 citations mean?
    Thank you very much and a happy new year
    Reply
    • Ludo Waltman January 3rd, 2020 12:34 pm
      I understand that this is confusing. The number of links and the total link strength are both based on the citation network that is being analyzed using VOSviewer. The 625 citations, on the other hand, refer to the total number of citations received by the publications of the author, counting all citations received from publications in the database that you are using (e.g., Web of Science, Scopus, or Dimensions). This also includes citations received from publications not included in the data set that you have provided as input to VOSviewer. This explains why the number of citations of an author can be larger than the author's total link strength.
      I hope this offers some clarification. Let me know if it is still not clear.
      Reply
  • Aynul December 30th, 2019 5:32 am
    What is the minimum number of documents to perform bibliometric analysis? please help me with any reference. Thanks a lot for helping along my journey.
    Reply
    • Ludo Waltman December 30th, 2019 7:58 am
      There is no minimum. Sometimes a bibliometric analysis based on just a few documents can already be insightful. VOSviewer visualizations usually become useful when one has at least a moderate number of documents, for instance 100 or 500, depending on the type of visualization that one is interested in.
      Reply
  • Saeedeh najafi December 25th, 2019 5:57 pm
    When i writing a thesaurus file, I'm getting an error that incorrect number of columns.
    I writing:
    Lable replace by
    Community communication
    ...
    Reply
    • Ludo Waltman December 26th, 2019 11:06 pm
      Please send your file to vosviewer@cwts.leidenuniv.nl and I will try to take a look at it.
      Reply
      • Saeedeh Najafi December 27th, 2019 6:53 am
        Thank you
        Reply
        • Cenk Demiroglu February 18th, 2020 5:44 pm
          Any solution here? I encounter the same problem. Thank you
          Reply
          • Cenk Demiroglu February 18th, 2020 6:03 pm
            Now I got rid of the error but cannot really see any changes in the map according to the thesaurus file.
            Reply
            • Ludo Waltman February 19th, 2020 9:36 am
              I can try to provide some help if you could send your files, along with a more detailed explanation of your problem, to vosviewer@cwts.leidenuniv.nl.
              Reply
  • Mansi Maheshwari December 25th, 2019 6:16 am
    Dear Ludo Waltman,
    I have a query regarding total link strength that has also been discussed previously in this forum. If in a co-citation map, the total link strength indicates the number of documents in which two authors/journals/documents co-occur, then what does the value of citations indicate.
    Thanks in advance
    Reply
    • Ludo Waltman December 25th, 2019 11:55 am
      Link strength indeed is the number of documents in your data set in which two references, two authors, or two journals co-occur in the reference list. Citations is the number of documents in your data set in which a reference, an author, or a journal occurs in the reference list.
      Reply
  • Serafim December 23rd, 2019 1:46 am
    Dear Ludo Waltman,
    First of all, I would like to congratulate you on the great work in developing this software.
    So, my question is: In january 2019, I used the VOSviewer to conduct a bibliometric analysis on a specific topic, applying the co-citation and co-occurrence analysis. However, now I am trying to update this study and I am having some difficulties in keywords co-occurrence analysis. In january, I verified that the keywords in the papers under analysis had an average publication year between 2010-2017; the database had articles published between 1993 and 2018, where most of them were recent articles. Yeasterday, I redid the keyword co-occurrence analysis developed in january ( adding to my initial database the articles that were published since january until now, and found an average publication year that range from 1940 to 2020. How is it possible since the oldest article in my database is from 1993?
    I would be grateful if you could help me to solve this problem.
    Reply
    • Ludo Waltman December 23rd, 2019 8:31 am
      I think this problem is due to so-called early access publications in Web of Science. These publications don't have a regular publication year and VOSviewer currently doesn't handle these publications in a correct way. The publication year of these publications is incorrectly set to 0 by VOSviewer. My recommendation is to make sure not to include any early access publications in your data exported from Web of Science. This should provide a workaround for your problem. In the next update of VOSviewer, the problem with early access publications will be fixed.
      Reply
  • Arun Saxena December 19th, 2019 7:09 am
    I am a PhD scholar at Jindal Global University, India.
    I need information on interpreting the graphs. For example,
    How do you calculate total link strength in different charts? What does its value really represent?
    How can I obtain CSV data on the charts - for example I want to obtain the co-occurence and co-citation data of keywords and journals respectively for quantitative analysis?
    The link for the AIDA booklet is not working. Can you please set it right?
    Thx
    Arun Saxena
    India
    Reply
    • Ludo Waltman December 20th, 2019 7:31 am
      Information about the total link strength can be found in Chapter 2 in the VOSviewer manual. The total link strength has also been discussed before in this forum. Please see the earlier questions on this topic.
      You can obtain the data underlying a map by clicking the 'Save' button and by saving your map in a VOSviewer map file and a VOSviewer network file. These are straightforward text files that contain all information about a map.
      Thanks for pointing out the problem with the AIDA booklet. We will try to fix this.
      Reply
  • Sofia Gomes December 16th, 2019 6:58 pm
    hello, i want to know if i can use vosviewer with another platforms tham WoS, scopus. I would like to use with RCAAP.
    Thank you
    Reply
    • Ludo Waltman December 16th, 2019 8:37 pm
      In addition to Web of Science and Scopus, many other data sources are supported by VOSviewer, such as Dimensions, PubMed, Microsoft Academic, Crossref, Europe PMC, Semantic Scholar, and OpenCitations. I am not familiar, however, with RCAAP.
      Reply
      • Sofia Gomes December 17th, 2019 6:52 pm
        Thank you! I will try to explore more. Congrats for your software.
        Reply
  • Aynul December 9th, 2019 6:00 am
    I want to make the co-citation analysis network with the dots as it is shown on "introduction to vosviewer" but it is coming as lines. how to do like dots are arranged in a cluster??
    Reply
  • Guiyu Li December 8th, 2019 4:30 pm
    Dear Ludo,
    Thank you for such good comment. I have edited the authors name and countries name to capital letter using this method. However, I have another problem when I open this edited map file, it did not display the lines between authors or countries. How can I fixed it?
    Thank you
    Reply
    • Ludo Waltman December 11th, 2019 11:12 pm
      The lines represent the links in your network. These links are not saved in a map file. They can be saved in a separate file, a so-called network file. When you open both your map file and the corresponding network file, you will see that VOSviewer will show the lines between the items in your map.
      Reply
      • Guiyu Li December 12th, 2019 3:55 am
        This suggestion really fixed my problem. Thank you so much for your comments.
        Reply
  • Shawn Flanagan December 5th, 2019 1:32 pm
    For the thesaurus file, if you want to merge multiple redundant terms, but one if the terms is correct, how do you do it without creating a new term? Right now it appears that a term in column one cannot appear as a replacement item in column 2.
    Reply
    • Shawn Flanagan December 5th, 2019 2:56 pm
      For instance, labels might include:
      1. MEP
      2. motor evoked potential
      3. motor evoked potentials
      4. motor evoked potential (mep)
      5. motor-evoked potential
      6. motor-evoked potentials
      I would like to merge these labels together, as they refer to the same thing, but use the term motor evoked potential, which already "exists" as a label.
      Reply
      • Ludo Waltman December 12th, 2019 4:46 pm
        In this case, your thesaurus file should look as follows:
        label replace by
        MEP motor evoked potential
        motor evoked potentials motor evoked potential
        motor evoked potential (mep) motor evoked potential
        motor-evoked potential motor evoked potential
        motor-evoked potentials motor evoked potential
        Reply
        • sana December 26th, 2019 2:14 pm
          how separate two column(lable column and replace by column)?
          i create a file like this but recieved error
          Reply
          • Ludo Waltman December 26th, 2019 11:02 pm
            You can use a tab as separator between the columns. See the VOSviewer manual for more details.
            Reply
  • John December 5th, 2019 3:50 am
    Dear Ludo,
    I wanted to run a co-citation analysis of cited references. As you know, some references appear with alternative labels. I tried to merge alternative wordings of a same reference in a map file but I could not do it. Because map file for "cited references co-citation" is not structured. When I open the map file in excel, it does not have unified column structure. Is there a way to clean/merge cited references?
    Also, I wanted to merge the names of some authors with alternative wordings. I used thesaurus file but it did not change the results although I used the "replace by" column and merged them. I had alternative names of a few same authors appearing in the results. Can you please recommend a solution? Many thanks
    Reply
    • Ludo Waltman December 13th, 2019 8:35 pm
      John, what is the data source that you are using?
      Reply
      • John December 14th, 2019 2:58 am
        I use Scopus. Map file for term co-occurrence is very good. When I use "text to column" in excel, it perfectly does it in a unified way across all the rows. But, this is not the case for the map files for "cited references co-citation".
        Thanks for your time.
        Reply
        • Ludo Waltman December 16th, 2019 5:18 pm
          In Scopus (unlike Web of Science), cited references do not have a standardized format. Therefore there are lots of inconsistencies in cited references and there is no easy way to fix this. For this reason, co-citation analyses based on Scopus data tend to be of little value.
          A thesaurus file can be used to clean and merge author names only if you perform an analysis of (cited) authors, not if you perform an analysis of cited references.
          Reply
          • John December 23rd, 2019 2:40 am
            Many thanks
            Reply
  • ROBERTO PORTELA DE CASTRO November 29th, 2019 7:58 pm
    Dear Ludo, Frist of all, congratulations for your. You dont have any idea how it is important in my master studies. Not only for me, but a lot of research colleagues. My question is about cluster. Is it possible to define and organize the words the will be show in each cluster?
    Reply
    • Ludo Waltman November 29th, 2019 8:22 pm
      Thanks for your kind words about the software!
      If you mean that you want to manually assign items to clusters, then this can be done by saving your map in a VOSviewer map file and by editing the 'cluster' column in this file in a spreadsheet program such as MS Excel.
      Reply
  • Mehmet Yildiz November 27th, 2019 5:54 am
    Dear Ludo,
    When working with large data sets, items can overlap and large items cover the smaller ones. So, some items disappear unfortunately. I wonder if it is possible with VOSviewer to manually relocate some of the disappearing items in the map.
    Thanks in advance for your truly valuable efforts
    Reply
    • Ludo Waltman November 28th, 2019 8:43 pm
      This cannot be done in the VOSviewer user interface. However, it can be done by saving your map in a VOSviewer map file and by then editing the x and y coordinates of items in this file. A map file can best be edited using a spreadsheet program such as MS Excel.
      Reply
  • Rafael k November 27th, 2019 4:12 am
    Dear Mr. Waltman, I would like to ask whether the fractional counting option works as replacement for the association strength normalization approach (or other of the available weight normalization options), or whether they complement one another. Thank you in advance! And congratulations on your exceptional work!
    Reply
    • Ludo Waltman November 28th, 2019 8:48 pm
      They are complementary. They do not replace each other.
      Reply
  • Aynul November 25th, 2019 10:19 am
    From Co-citation analysis, I can know that a certain article has been cited 20 times or whatever the number is. But how can I know which published articles have cited that certain article?
    TIA for help and cooperation.
    Reply
    • Ludo Waltman November 25th, 2019 10:27 am
      At the moment, there is no easy way in VOSviewer to obtain this information.
      Reply
  • Shawn Flanagan November 20th, 2019 3:26 pm
    Hello,
    Where can I find the thesaurus_terms.txt file?
    Reply
    • Ludo Waltman November 20th, 2019 7:51 pm
      In the ZIP archives that can be downloaded from https://www.vosviewer.com/download.
      Reply
  • Mehmet Yildiz November 17th, 2019 5:08 am
    Dear Ludo Waltman,
    Thanks for answering all the questions.
    I have a question. I run a co-occurrence analysis based on title and abstract. When I choose minimum 3 occurrence, I get 186 terms. When I check them, I see some alternative use of same phrases like:
    "leader mindfulness" and "leaders mindfulness",
    "leader competency" and "leader skill",
    "follower" and "subordinate"
    "relation" and "relationship"
    Is there any way that I can integrate them into one expression? I mean for instance, can I transform "leader capability" into "leader skill".
    I can find and replace them in the excel file but I am not sure for the following: Are these terms ( leader capability) adjacent in the abstract and title or, are they appearing in the same title or abstract but seperate from each other (leader [............] capability), not adjacent. Can you please advice?
    The following article says they used an R script to combine variants of same expressions, but I could not find how they did it.
    https://doi.org/10.1016/j.leaqua.2019.06.001
    I would really appreciate if you could help with this? Thanks in advance.
    Reply
    • Ludo Waltman November 17th, 2019 12:09 pm
      If you are able to determine which terms you would like to be merged, you can create a thesaurus file to tell VOSviewer it should merge these terms. More information about thesaurus files can be found in the VOSviewer manual.
      Reply
      • Mehmet Yildiz November 19th, 2019 1:28 pm
        Many thanks for the explanation.
        Reply
  • stephanie November 12th, 2019 4:07 pm
    Hi
    I have a question related to citing journals: if I am studying a specific journal's body of literature, how is it possible to find the other journals that are citing 'my' journal? I know on web of science for example how to get to that information but I was curious to see if I can also get it through VOSviewer, for example to get a map. Thx in advance
    Reply
    • Ludo Waltman November 14th, 2019 7:58 pm
      This is somewhat difficult. When you use a data source such as Web of Science, Scopus, or Dimensions to download data for a particular journal, you don't obtain data on other journals that cite the focal journal. Since this data is missing, VOSviewer is unable to visualize how your focal journal is cited by other journals. You could download data for all journals in a particular field and based on this data you could then create a citation-based map of journals. This will give some insight into the way in which a specific focal journal has citation relations with other journals in the same field.
      Reply
  • Aynul November 8th, 2019 3:34 am
    Under "Types of analysis" i dont get active for "Bibliometric coupling", "citation" and "co-citation" options. Only co-occurrence and co-authorship are active. So i cannot perform analysis. Whats the remedy please?
    Reply
    • Ludo Waltman November 8th, 2019 7:43 am
      What kind of data are you working with? In the case of Web of Science and Scopus data, you need to make sure that references are included in the data that you download from these data sources. There are also data sources that don't provide references at all (e.g., PubMed and reference managers). When the latter data sources are used, it is not possible to create citation-based maps. See also the VOSviewer manual for more details.
      Reply
  • Anuja November 7th, 2019 6:44 pm
    Dear Mr. Waltman,
    I have .csv files exported from scopus and I want to conduct co-citation analysis. Although the options for analysis is inactive. Is there any way I can analyse co-citation network through .csv files.
    Thank You
    Anuja Joseph
    Reply
    • Ludo Waltman November 7th, 2019 7:11 pm
      You need to make sure to include references when exporting data from Scopus. This will enable you to perform co-citation analysis.
      Reply
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