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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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  • giuseppe vito December 4th, 2020 12:12 pm
    Hi Ludo, sorry for bothering you but I feel the need of a comparison and a comfort: what do you think about coupling and mapping references on the basis of keywords (column DE in a WoS file) and not (or also) on the basis of cited references (column CR)? Thanks for your attention and my best wishes for the upcoming holidays.
    Reply
  • Mihiretu Kebede December 4th, 2020 11:15 am
    Do you have an R package for VOSviewer? It will be a great hit.
    Reply
  • Mirian Moreira December 4th, 2020 2:37 am
    Hi!
    Could you help me with a situation? I am using a thesaurus with the intention of to combine some keywords that have the same meaning, however, I am not successful in the sum of the occurrences with some of these words. For example, I am trying to combine “human - 20 occurrences” with “humans - 17 occurrences”, however replacing “human” with “humans” I get 20 occurrences and not 37. I emphasize that this failure does not occur with so many other words used in the same thesaurus. In these cases, the sum occurs as expected. I appreciate if you can help me.
    Reply
  • Sheng Liu December 1st, 2020 8:34 am
    Hello, how can I set not to convert to lowercase letters in the process of importing data?
    Reply
    • Ludo Waltman December 1st, 2020 10:49 am
      The conversion from upper case to lower case cannot be turned off. It is necessary because some data sources use upper case and lower case in an inconsistent way. To handle these inconsistencies, VOSviewer converts all upper case characters to lower case when a new map is created.
      After you have created a map, you can save the map in a VOSviewer map file. This file can then be edited in a spreadsheet program such as MS Excel. By editing the labels in the 'label' column, you can convert lower case characters to upper case.
      Reply
  • Rajesh Godasu November 30th, 2020 10:16 pm
    Hi,
    is there a video on how to upload the maps online?
    Reply
    • Ludo Waltman December 1st, 2020 12:04 am
      I am afraid there is no such video. By the way, in the near future, we expect to release a web-based version of VOSviewer, which will make it easier to make maps available online.
      Reply
  • Ahmad Heru Romadhon November 29th, 2020 10:48 am
    like this to aplication
    Reply
  • Philip November 29th, 2020 3:10 am
    Ludo
    In a document co-citation analysis what is the conceptual difference in the measure of influence between citations and total link strength?
    Assume for example that two documents have the same or similar level of citations, but one has much greater link strength. How does one interpret that difference?
    Thanks.
    Philip
    Reply
    • Ludo Waltman November 29th, 2020 9:20 am
      If two documents have a similar number of citations, but one has a much higher total link strength than the other, this means that the former document is much more strongly connected, through co-citation links, with other documents included in the co-citation network. The latter document has a more peripheral position in the network.
      Reply
  • Whaner Endo November 24th, 2020 12:13 am
    Dear friends,
    First of all, thanks for this increadible tool!
    I was wondering if something changed in VOSviewer or in Dimensions last week, because suddenly I started to get the error message: "Error while reading Dimensions file 'name of the file' (line XXX): Incorrect number of columns".
    I'm using the same workflow as I always used... Any hint?
    Best,
    Whaner Endo - University of Sao Paulo (Brazil)
    Reply
    • Ludo Waltman November 26th, 2020 12:03 am
      Recently some changes were made to the file export feature in Dimensions. The problem that you mention is due to these changes. A new version of VOSviewer (version 1.6.16) has just been released. In this version the problem has been fixed.
      Reply
      • Whaner November 26th, 2020 2:03 pm
        Dear Ludo,
        Back to normal... Thank you very much! 8-)
        Best,
        Whaner
        Reply
  • Abeer November 23rd, 2020 8:59 pm
    Hello team,
    I got an error window box, it says:
    Error while reading VOSviewer map file (line 1): FN ClARIVATE ANALYTICS WEB OF SCIENCE is not a valid column header.
    I tried to save the WOS file as plaintext and as tap-delimited (win). also, I tried using the web version of VOSviewer ...got the same error window box!
    looking forward to your adivce!
    Reply
    • Ludo Waltman November 25th, 2020 11:50 pm
      If you send your file to vosviewer@cwts.leidenuniv.nl, I will take a look at it and try to offer advice.
      Reply
  • Jennifer Zhao November 22nd, 2020 10:47 pm
    Hello,
    I am working on a set of publications of a university department. In the bibliographic coupling analysis and the co-citation analysis, the same item (e.g. the journal "Nature") in respective visualization ("sources" in the former analysis and "cited sources") shows a different number of citations. Could you explain why? The "documents" and "citations" are the same in the citations analysis and bibliographic coupling analysis.
    In addition to finding out the top journals that the researchers have published in, can VOSviewer present the journals that are most-frequently cited in a set of publications?
    Thanks for your time!
    Jennifer
    Reply
    • Ludo Waltman November 22nd, 2020 11:44 pm
      In the case of citation analysis and bibliographic coupling analysis, the number of citations is the total number of citations received by a journal in the database that you are working with (e.g., Web of Science or Scopus). In the case of co-citation analysis, the number of citations is the total number of citations received by a journal in the documents provided as input to VOSviewer.
      Co-citation analysis enables you to identify the most frequently cited journals in a given set of documents.
      Reply
      • Jennifer Zhao November 25th, 2020 5:40 pm
        Hi Ludo, I am thankful for the explanation. It's very helpful!
        I have a question about the distance between two items in a network. For example, in a co-authorship visualization, how does VOSviewer calculate the distance between two authors? How does it determine clusters?
        Thanks in advance!
        Jennifer
        Reply
  • Arie November 17th, 2020 11:43 pm
    could you help me please?
    I was trying to make a thesaurus file txt from excel file. I already converted the file but when I clicked next in my VoS suddenly a warning pop-up message occured "column header is empty". I had made label and replace by in the first line of my excel file. what should I then?
    Reply
    • Ludo Waltman November 18th, 2020 7:09 am
      Your file probably contains more than two columns. You need to make sure it contains only two columns. If you are unable to fix the problem, then feel free to send your file to vosviewer@cwts.leidenuniv.nl. I will then try to take a look at it.
      Reply
      • Arie November 21st, 2020 11:37 am
        Many thanks for your suggestion, I will try it.
        Reply
  • Eve November 12th, 2020 9:45 pm
    The manual has mentioned that I can clean my dataset to get rid of repeating terms (synonyms) as well as merging terms using a thesaurus file. However the manual did not explain how a VOSviewer thesaurus file is created. I am kindly asking for assistance with steps taken to create the thesaurus file compatible with VOSviewer?
    Reply
    • Ludo Waltman November 14th, 2020 3:47 pm
      A thesaurus file needs to be created manually outside VOSviewer. This can best be done using a spreadsheet program such as MS Excel. Make sure to save the file as a tab-delimited text file (not as a spreadsheet file).
      Reply
  • Asha Nair November 3rd, 2020 3:51 pm
    How do i input bibexcel net file to vosviewer?
    Thanks and Regards,
    Asha
    Reply
    • Ludo Waltman November 15th, 2020 9:11 am
      Click the 'Create' button on the 'File' tab, choose the option 'Create a map based on network data', go to the 'Pajek' tab, and select your NET file as a Pajek network file.
      Reply
  • Cesar França October 30th, 2020 5:38 pm
    Hi! I am trying to use the data available at Semantic Scholar but could not find how to retrieve it as a DOI file.
    It seems I must use and Semantic API but I was not able to find the details of how to proceed.
    Would you mind to give me some guidance?
    Thanks,
    Cesar
    Reply
  • Tejas Adsul October 28th, 2020 12:30 am
    Hi! I'm wondering if there is a way to extract the distance between the concepts from the co-occurrence map of a text-based data. Since VOSviewer is supposed to give distance-based graphs, I'd like to have a scale based on which I can tell the relative distance between two concepts. Thank you!
    Reply
    • Ludo Waltman November 15th, 2020 9:17 am
      My recommendation is to save your map in a VOSviewer map file (using the 'Save' button on the 'File' tab). The map file can be opened in a spreadsheet program such as MS Excel. The 'x' and 'y' columns in the file provide the coordinates of each item in your map. Based on these coordinates you can calculate the distances between the items.
      Reply
  • Phuong Nguyen October 25th, 2020 5:22 pm
    Hello, i am trying out the newest version 1.6.15, but i find out that it is now missing the choice of analyze the data by citation and co-citation. Is that any way i can active it? Or do i need to find the older version of this app to have those choice?
    Reply
    • Ludo Waltman November 15th, 2020 9:28 am
      You need to make sure that the data provided as input to VOSviewer includes data on references. When working with data exported from Web of Science or Scopus, reference data by default is not included. When exporting data from Web of Science or Scopus, you need to explicitly indicate that reference data should be included. This will enable you to create citation-based maps in VOSviewer.
      Reply
      • Phuong Nguyen November 17th, 2020 2:50 am
        Yes, that is my mistake, the RIS file export from mendeley do not include the citation data. Thank you for your response!
        Reply
  • maryam vizheh October 25th, 2020 10:22 am
    Hello. I have an important question. When we formulate a search strategy whatever very precise, it is likely that so many articles will enter to our search results that they are not related to our topic. In the systematic review we assess every single abstract and title, however when we want to work with VOS VIEWER how we can be sure that all included results are exactly related to our purpose of the study? Please guide me. Thank you
    Reply
  • Liza October 19th, 2020 2:58 pm
    Good day
    I am doing a term co-occurrences map based on text data. I am confused about how the link strength is calculated. The occurrence of word A is 35 and the occurrence of word B is 16, and their total link strength is 72. I thought the link is the number of times the two words co-occurred, but word A cannot co-occur with word B 72 times because it only occurred 35 times, and word B only occurred 16 times.
    If someone can please assist on how the total link strength is calculated, please.
    Reply
    • Ludo Waltman October 19th, 2020 4:04 pm
      Did you use binary counting or full counting?
      Reply
      • Liza October 26th, 2020 9:10 am
        full counting
        Reply
        • Ludo Waltman November 15th, 2020 9:37 am
          In the case of full counting, co-occurrences are counted in a multiplicative fashion. Suppose for instance that in a certain document term A occurs 2 times and term B occurs 3 times. This will be counted as 2 x 3 = 6 co-occurrences of terms A and B. This explains why the total number of co-occurrences of terms A and B can be larger than the total number of occurrences of both term A and term B. In the case of binary counting, the total number of co-occurrences of two terms cannot be larger than the total number of occurrences of each of the terms.
          Reply
  • New October 19th, 2020 11:47 am
    Hello,
    How can I combine two similar keywords?
    For example, there are
    absorptive capacity
    absorptive-capacity
    It is definitely one term.
    thank you
    Reply
    • Ludo Waltman October 19th, 2020 3:08 pm
      A thesaurus file can be used for this. Please see the VOSviewer manual for more information about thesaurus files.
      Reply
      • New October 19th, 2020 5:49 pm
        Thank you.
        Do we construct thesaurus file ourselves?
        In the manual it is written:
        "For examples of thesaurus files, see the files thesaurus_authors.txt and thesaurus_terms.txt".
        I do not understand how to obtain them.
        Reply
        • Ludo Waltman October 19th, 2020 9:47 pm
          You need to create thesaurus files yourselves. The thesaurus files that you mention are included when you download VOSviewer from https://www.vosviewer.com/download. However, these files just serve as examples.
          Reply
          • New October 21st, 2020 5:03 pm
            Thank you.
            Reply
  • Mireia Tintoré October 16th, 2020 11:40 am
    Dear authors,
    How can I provide a RefWorks file as input to VOSviewer? Thank you very much,
    Mireia
    Reply
    • Ludo Waltman October 19th, 2020 4:01 pm
      Yes, RefWorks files are supported (even though they offer only limited possibilities). You need to click the 'Create' button in VOSviewer, you then need to choose the option 'Create a map based on bibliographic data' or 'Create a map based on text data', followed by the option 'Read data from reference manager files', and you then need to go to the 'RefWorks' tab.
      Reply
      • Mireia Tintoré October 21st, 2020 5:08 pm
        Thank you
        Reply
  • Bénédicte Madon October 15th, 2020 5:51 pm
    Dear Dr Waltman,
    is there a limited number of files (e.g. in plain text) that can be selected to do the mapping?
    Best wishes
    Bénédicte
    Reply
    • Ludo Waltman October 17th, 2020 12:23 am
      When creating a map based on data from, for instance, Web of Science, Scopus, or Dimensions, it is possible to select multiple files at the same time (using the Control key). VOSviewer will then process all selected files. You don't need to manually merge your files before providing them as input to VOSviewer.
      Reply
  • Yunjin October 13th, 2020 6:53 pm
    Hi,
    I'm trying to merge the search results from multiple sources including WOS, Scopus, and pubmed.
    I was wondering if there is any available format for this or code to merge files.
    Thanks,
    Yunjin
    Reply
    • Ludo Waltman October 17th, 2020 12:15 am
      Unfortunately there is no easy way in which this can be done.
      Reply
    • Aynul October 18th, 2020 6:25 pm
      I was also looking for this but unfortunately nothing is found helpful
      Reply
  • don kirkendall October 9th, 2020 6:28 pm
    Just learned about VOSviewer today. Use a Mac, OS Catalina (10.15.1). Downloaded and extracted the zip file. When i click on VOSviewer.app, this window pops up:
    “VOSviewer.app” can’t be opened because Apple cannot check it for malicious software.
    This software needs to be updated. Contact the developer for more information."
    Any suggestions on how to proceed?
    Reply
    • don kirkendall October 9th, 2020 7:13 pm
      Success. I have been able to open the VOSviewer. Restarting my computer was the step I was missing.
      Reply
      • Anita October 11th, 2020 5:49 pm
        How did you solve your problem? I am facing the same
        Reply
  • Christian Jehle October 8th, 2020 6:13 pm
    Hi there,
    On my new Windows system VOSviewer doesn't start, saying "This applicatiopn requires a Java Runtime Environment 1.8.0".
    Actually, I've installed AdoptOpenJDK with JAVA_HOME and Path variables set properly.
    Is there any convenient way to go on without the Oracle Java RE?
    Best,
    Christian
    ---
    F:>java -version
    openjdk version "11.0.8" 2020-07-14
    OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.8+10)
    OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.8+10, mixed mode)
    Reply
    • Christian Jehle October 14th, 2020 2:38 pm
      Ok, just found out:
      "VOSviewer 1.6.15 for other systems" works fine. To start the programme use java -jar VOSviewer.jar (for example in a *.bat file)
      Best,
      Christian
      Reply
  • Christian Jehle October 8th, 2020 6:10 pm
    Hi there,
    On my new Windows system VOSviewer doesn't start, saying "This applicatiopn requires a Java Runtime Environment 1.8.0".
    Actually, I've installed AdoptOpenJDK with JAVA_HOME and Path variables set properly.
    Is there any convenient way to go on without the Oracle Java RE?
    Best,
    Christian
    ---
    F:>java -version
    openjdk version "11.0.8" 2020-07-14
    OpenJDK Runtime Environment AdoptOpenJDK (build 11.0.8+10)
    OpenJDK 64-Bit Server VM AdoptOpenJDK (build 11.0.8+10, mixed mode)
    Reply
  • Aynul September 30th, 2020 7:17 pm
    Within a selected dataset, how can I find:
    which documents are co-cited and they are co-cited by which other documents so that I can find their co-citation number too. Waiting for your reply.
    Reply
  • Andy Yeung September 30th, 2020 4:21 am
    Hi Professor Waltman,
    Currently the output data contains average citations (per publication) for the analyzed "terms", authors, countries, journals, etc. How can we find out and report the standard deviation (SD) or the median? Thank you.
    Best regards,
    Andy
    Reply
    • Ludo Waltman October 11th, 2020 5:45 pm
      I am afraid VOSviewer doesn't support the standard deviation and the median. It is not possible in VOSviewer to obtain this information.
      Reply
  • Mostafa September 25th, 2020 7:56 am
    Hi,
    I am Mostafa from Monash university. In keywords co-occurrence analysis, in order to make the mapping more meaningful and consistent I have unified the keywords to reflect their associated concept. But there are keywords which don't really convey a concept/topic in my bibliometric analysis. I am wondering if deselection of these keywords may affect the authenticity and correctness of the analyses in VOSviewer?
    Thanks,
    Kind regards.
    Reply
    • Ludo Waltman September 25th, 2020 7:59 pm
      From my point of view, leaving out specific keywords is perfectly fine. Of course, when you report your analysis, you need to explain and justify your choice to leave out certain keywords.
      Reply
      • Mostafa September 27th, 2020 6:43 am
        Thanks for the reply. Yes I have justified the reason why I have deselected them both in the body of the review paper and the supplementary information file.
        Again, well-done on your great job and keep up your good works.
        Best wishes.
        Mostafa.
        Reply
  • Mostafa September 25th, 2020 7:49 am
    Hi,
    I am Mostafa from Monash university. In keywords co-occurrence analysis, in order to make the mapping more meaningful and consistent I have unified the keywords to reflect their associated concept. But there are keywords which don't really convey a concept/topic in my bibliometric analysis. I am wondering if deselection of these keywords may affect the authenticity and correctness of the analyses in VOSviewer?
    Thanks,
    Kind regards.
    Reply
  • Andy Yeung September 15th, 2020 8:51 am
    Dear Professor Waltman,
    Would future versions of VOSviewer consider data slicing? It will be much more convenient if we can slice the whole dataset into different time periods, or different publication types, etc. Especially when the dataset is large, it is time-consuming to re-download from WoS based on different filters. Thank you for your consideration.
    Best regards,
    Andy
    Reply
    • Ludo Waltman September 16th, 2020 9:19 am
      Thanks Andy for this suggestion. This is indeed on our to-do list, although I cannot promise we will be able to implement this in the near future. Please note that there are various data sources, such as Microsoft Academic, which VOSviewer accesses through their API (rather than by processing text files downloaded manually through a web interface). For these data sources VOSviewer already offers possibilities for data slicing.
      Reply
      • Andy Yeung September 16th, 2020 4:14 pm
        Thanks for the suggestion!
        Reply
  • Javier Guerrero September 11th, 2020 7:20 pm

    Hi,
    I have two data sets from scopus, publications in a two different journals in the same field. I'm trying to create a co-authorship network and I stumble in a little issue, same author with different name format. I have for example 'Adelekan M' in one data set and Adelekan M.L. in the other one (same author ID), and therefore producing each one a different co-authorship network. But if I try to modify the .cvs file, deleting or adding a character I get the:
    I0Exception reading next record: java.io.I0Exception: (line 2) invalid char between encapsulated token and delimeter
    any advice on how to get around this?
    cheers,
    Javier
    Reply
    • Ludo Waltman September 11th, 2020 8:02 pm
      Modifying Scopus CSV files is possible in principle, but usually causes all kinds of problems in practice. There is an easier solution to your problem, which is to use a so-called thesaurus file. See the VOSviewer manual for more information about thesaurus files.
      Reply
      • Javier Guerrero September 11th, 2020 8:42 pm

        Many thanks! will do
        Best
        Javier
        Reply
  • Oak September 9th, 2020 12:15 pm
    I am new to VOSViewer and my attempts to download it on to my pc has not been successful. I am using a Mac running on MacOS Catalina.
    I've followed Nees' guide on how to install it but it is still not working. Any assistance, please?
    Reply
  • Javier Guerrero September 7th, 2020 7:12 pm

    Hi, I try to combine two .cvs extracted from scopus, each one works fine, but as soon as I combine I get the I0Exception reading next record: java.io.I0Exception: (line 2) invalid char between encapsulated token and delimeter
    I have tried with really simple searches and complex ones, and each file works fine, but as soon as I try to merge two of them the error pops up.
    Thanks,
    Javier
    Reply
    • Ludo Waltman September 7th, 2020 7:16 pm
      VOSviewer is able to open multiple Scopus CSV files at the same time (use the Control key to select multiple files), so there is no need to manually merge your files.
      Reply
      • Javier Guerrero September 7th, 2020 7:33 pm

        Thanks :)
        Reply
  • Irene Garcia August 29th, 2020 1:57 pm
    Hi!
    I would like to know if the program allows to create a network with the data from two different databases.
    For example: to create a network about the kyewords/terms from WoS and Scopus in the same graphic. Is it possible? I have checked the manual and the tutorial video and I could not find this information.
    I really apreciate your help and time.
    Kind regards,
    Reply
    • Ludo Waltman August 29th, 2020 7:03 pm
      VOSviewer doesn't provide support for combining data from multiple data sources.
      Reply
  • Pavitra Dhamija August 24th, 2020 12:42 pm
    Dear Prof. Nees and Prof. Ludo
    Good Day ! I have recently started working on VOSviewer and just loving it.
    However, I am facing a problem that; all of the types of analysis are not enabled in the software in my system.
    For example:
    Co-authorship; Co-occurrence are enabled
    Citation; Bibliographic coupling; Co-citation are not enabled. I cannot use these three types.
    Kindly extend your esteemed guidance to solve this issue.
    Regards
    Pavitra Dhamija
    Post Doc
    University of Johannesburg
    South Africa
    Reply
    • Ludo Waltman August 24th, 2020 4:06 pm
      When exporting data from Web of Science or Scopus, you need to make sure to include data on the references of publications. To do so, follow the instructions on p. 27 in the VOSviewer manual. I expect this will solve your problem.
      Reply
  • Shelley E Olds August 18th, 2020 9:24 pm
    I want to use the term viewer to analyze my WOS results in a few ways. I've made a nice term map from the results from a rather 'complicated' WOS search. I would like to be able to select terms in the viewed map and see the articles that are associated with that term. Is there a way to do this?
    Then I want to analyze two subsets of WOS datasets - one subset includes the articles that have passed my criteria for title and abstract; the second subset are those that fail. My goal is to identify if there are patterns in the search terms that led to an article passing vs failing.
    It seems like VOSviewer has this association but is hidden away . In the bibliographic maps, the articles can be seen. Your help is much appreciated!
    Reply
    • Ludo Waltman August 22nd, 2020 10:07 pm
      Getting the relations between terms and documents is possible in VOSviewer, but this feature is somewhat hidden. In the final step of the 'Create Map' wizard, a table is presented listing the terms to be included in your map. When you right-click on this table, a context menu will appear that offers an option for exporting the document-term relations to a text file. There is also an option for exporting the terms to a text file. Combined with the original WoS file that was provided as input, this provides all data needed to determine which terms occur in which documents. To further analyze the data, you probably need to use a spreadsheet program or a tool like R or Python.
      Reply
  • Xueting You August 12th, 2020 9:39 am
    When I open a .net file by Pajek, then I use the "VOS Mapping" function of Layout, the application tell me that"VOS Mapping cannot be applied to disconnected networks." What should I do to solve this problem? I'm looking forward for your replay, and thanks very much for your help.
    Reply
    • Ludo Waltman August 16th, 2020 11:45 am
      If you send your Pajek network file to vosviewer@cwts.leidenuniv.nl, I will take a look at the file and try to offer advice.
      Reply
  • Xueting You August 12th, 2020 9:31 am
    I have opened a .net file by Pajek, then I used the "VOS Mapping" function of Layout, but the software told me that "VOS Mapping cannot be applied to disconnected networks." What should I do to solve this problem? I'm looking fordward to your replay, and thanks very much for your kindly help.
    Reply
  • xiangqi August 11th, 2020 10:24 am
    it shows that vosviewer close unexpectedly, help me, please
    Reply
  • sheikh shueb August 8th, 2020 9:18 am
    I am not able to use VosViewer for analyzing large data set consisting of about 50 thousand records downloaded from Web of Science. plz help?
    Reply
  • Mohammad August 7th, 2020 2:46 am
    Hi,
    I need your assistance in clearing an error in a .csv file containing data..
    This is the error I keep receiving when analysing the data:
    'Error while reading Scopus file 'scopus.csv' : null
    Thanks.
    Reply
    • Ludo Waltman August 7th, 2020 10:00 am
      Could you please send your file to vosviewer@cwts.leidenuniv.nl? I will then take a look at your problem.
      Reply
  • Omwoyo Bosire Onyancha July 28th, 2020 12:05 pm
    Hi Ludo,
    Thanks for re-enabling my access to this site after my IP was blocked. Please tell me - how can one determine the distance between two countries in a co-authorship network?
    Reply
    • Omwoyo Bosire Onyancha July 28th, 2020 12:10 pm
      And what does that distance mean?
      Reply
      • Ludo Waltman July 29th, 2020 8:45 am
        Do you mean the distance between two countries in a map of a co-authorship network? In such a map, the distance between two countries approximately reflects the number of co-authored publications of the countries (after normalizing for the total number of co-authored publications of each of the two countries). In general, the closer two countries are located to each other, the larger their number of co-authored publications.
        Reply
        • Omwoyo Bosire Onyancha August 7th, 2020 10:40 am
          Thanks Ludo for the response. Does a co-authorship network provide the distance (in whatever metric) between co-authors (individuals, countries or institutions)? All I get is links, link strength, papers, and citations (with normalized citations). I do not see any metric that may explain the distance.
          Reply
          • Ludo Waltman August 9th, 2020 3:17 pm
            Could you explain what you mean by the distance between co-authors, perhaps by giving an example? At the moment it is not clear to me what you have in mind.
            Reply
            • Omwoyo Bosire Onyancha August 9th, 2020 11:46 pm
              Let me put it this sir: is there a metric to measure a distance between two nodes in a network?
              Reply
              • Ludo Waltman August 10th, 2020 7:11 am
                In VOSviewer, no such metric is provided.
                Reply
                • Omwoyo Bosire Onyancha August 10th, 2020 11:34 am
                  Thanks for the clarification
                  Reply
  • Dan July 26th, 2020 5:16 am
    Hello,
    I'm doing a bibliographic coupling analysis of the document level.
    If I have a document with 20 links and a total link strength 3.
    What does that mean?
    Reply
    • Ludo Waltman July 26th, 2020 8:44 am
      Are you using full counting or fractional counting?
      Reply
      • Dan July 26th, 2020 1:06 pm
        fractional counting
        Reply
        • Ludo Waltman July 27th, 2020 11:17 am
          The total link strength equals the sum of the strengths of the bibliographic coupling links of your focal document with other documents in your bibliographic coupling network. Using full counting, the total link strength will always be greater than or equal to the number of links (since each link has a strength of at least 1), but using fractional counting (see https://doi.org/10.1016/j.joi.2016.10.006 or https://arxiv.org/abs/1607.02452) this doesn't need to be the case.
          Reply
          • Dan July 27th, 2020 12:30 pm
            thank you very much
            Reply
  • Jana Keller July 23rd, 2020 11:24 am
    Hi,
    I would like to ask you if there is a way to save the map generated in a format that can be opened again in Vosviewer.
    Thank you in advance.
    Reply
    • Jana Keller July 23rd, 2020 12:16 pm
      I'm sorry, the solution is so simple:
      I now realized that you have to save both the network and the map file as .txt, then you can open it again in VOSviewer.
      Thanks for this great tool!
      Reply
  • Iloni July 16th, 2020 4:24 am
    Hello
    How do I see the articles that are referenced in a node? For example, in a grouping of citations by countries, how to extract which articles belong to a country and consequently make up the node?
    Reply
    • Ludo Waltman July 18th, 2020 8:46 am
      This information can be obtained in the last step of the 'Create Map' wizard. You need to right-click on the table listing the countries. A context menu will appear in which you can choose to export the relations between countries and documents. Using this option, the relations between countries and documents will be exported to a text file.
      Reply
      • Iloni July 19th, 2020 2:35 am
        Thanks for the answer
        but I still need some help. on the generated map we have the display of several countries. I need to know what research is related to each country. For example, Italy had 40 articles. How to generate a list with 40 articles related to Italy?
        Reply
        • Ludo Waltman July 19th, 2020 1:32 pm
          The only way to get this information is the way I explained in my previous answer. Unfortunately, VOSviewer currently doesn't offer an easier way to get this information.
          Reply
  • Ayushi July 10th, 2020 5:54 pm
    i could not find the VOSviewer.jar file in the downloaded file. can you please help me out
    Reply
    • Ludo Waltman July 13th, 2020 2:19 pm
      The JAR file can be downloaded using the link 'Download VOSviewer 1.6.15 for other systems' on the download page.
      Reply
  • Bosire July 8th, 2020 2:12 pm
    Can somebody please assist me on how to resolve this error that keeps popping up when analysing WoS data?
    "Error while reading Web of Science file 'savedrecs'.text (line 22): Multiple C1 fields".
    It seems like WoS started duplicating the C1 fields for records?
    Reply
    • Ludo Waltman July 22nd, 2020 5:14 pm
      Could you please send your Web of Science file to vosviewer@cwts.leidenuniv.nl? I will then take a look at your file and try to offer advice.
      Reply
      • Camila Silva September 25th, 2020 10:32 pm
        I've had a similar error "Error while reading PubMed file 'pmc_result (2).txt' (line 57): Multiple TI fields". Please, could someone help me?
        Reply
  • María July 4th, 2020 9:18 am
    Hello,
    I want to congratulate you for your efforts creating this tool and helping us with our questions.
    Could you explain the difference on the relationship items have with each other in terms of links and in terms of clusters?
    If the co-word analysis indicates that word A have a link with B it means that both are used together in a text? If so, why could they belong to different clusters? Considering the distance between items is the times they are used together, then how to understand the clustering criterium?
    Maybe it's too easy but I can't get the difference even reading the manual on how can we interpret clusters Vs links or Vs distance between items?
    Thank you so much for your time!
    Greetings
    Reply
    • Ludo Waltman July 18th, 2020 10:33 am
      The proximity of items in a map approximately indicates the relatedness of the items in terms of co-occurrences. Likewise, a cluster indicates a set of items that are relatively strongly connected in terms of co-occurrences. A technical explanation of the clustering criterion can be found in the book chapter available at the top of this page. The essence is that items belonging to the same cluster have a relatively high likelihood of being connected by co-occurrence links, while items belonging to different clusters have a relatively low likelikehood of being connected by co-occurrence links. Note that there will almost always be items that are not assigned to the same cluster even though they are connected by co-occurrence links. This cannot be avoided, unless all items in a map are assigned to the same cluster.
      Reply
      • María August 12th, 2020 12:21 am
        Thank you so much!
        Reply
  • Bosire June 29th, 2020 9:30 pm
    On another issue Prof..
    Have you been able to find out if it is possible for one to increase the memory in macbook laptops? I have tried in vain. The VOSviewer is unable to analyse 69,000 records at one go.
    Reply
  • Bosire June 28th, 2020 10:31 pm
    I need your assistance in clearing an error in a .csv file containing data..
    This is the error I keep receiving when analysing the data:
    'Error while reading Scopus file 'scopus.csv' : IOException reading next record: java.io.IOException: (line 1280) invalid char between encapsulated token and delimiter
    Thanks.
    Reply
    • Ludo Waltman June 29th, 2020 7:49 pm
      This problem is caused by a bug in the Scopus CSV export. Usually the problem can be fixed by leaving out certain types of information from the export. Recently it turned out that the indexed keywords cause problems, so you could for instance try to leave out those. Hopefully the Scopus team will soon fix the bug.
      Reply
      • Bosire June 29th, 2020 9:07 pm
        Thanks Ludo for your assistance. I have realised that the problem was specifically associated with conferences.. Articles seem to be find.
        Reply
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