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 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
  • 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
  • Dario Sablone November 5th, 2019 12:11 am
    Dear Mr. Waltman,
    I am making a co-citation analysis of a csv file from Scopus. I have also created a Thesaurus file. The problem is that the software does not read the Thesaurus file correctly: it changes the labels to just some of the articles and not to all those that should be replaced by a correct one. If you know any reason why this happens I would be happy to hear it.
    Thank you very much,
    Dario Sablone
    Reply
    • Ludo Waltman November 6th, 2019 7:39 am
      Please send your files to vosviewer@cwts.leidenuniv.nl. I will then try to help you with this.
      Reply
  • Adel Mohebbi November 1st, 2019 6:12 am
    Dear Ludo Waltman,
    I have a CVS file from scopus and a plain text from Web Of Science . How can I use both of them in VOSviewer ?
    Or, what Kind of export format do u propose to use web of science and scopus data base(in one file for example) together in vosviewer.
    Thank you very much
    Reply
    • Suzi Dias November 1st, 2019 1:41 pm
      Dear Adel,
      I have the same question.
      When you get it, can you share with me, please?
      my e-mail is dias.suziferreira@gmail.com.
      Thank you very much.
      Reply
      • Ludo Waltman November 2nd, 2019 10:02 am
        Unfortunately, there is no easy way to combine data from Web of Science and Scopus. Combining the two data formats is highly challenging. In general, my recommendation is to work with data from a single data source.
        Reply
  • Bob Adler October 28th, 2019 7:12 pm
    Question from a newb...
    How does one download 7,800+ search citations from PubMed, without selecting them one at a time or exporting and then reassembling multiple clipboards with what appears to be 500 citation clipboard limit or the 200 citation display limit? Arrgh!
    Have to be certain this question has been asked before and someone has answer / method
    Thank you very much
    BOB
    Reply
    • Ludo Waltman October 28th, 2019 9:59 pm
      I am afraid I don't understand your question. It is easy to export large numbers of records from PubMed. You need to export the records in a MEDLINE file, as explained in the VOSviewer manual (p. 27-28). I don't know what you mean by clipboard and display limits.
      Reply
      • Bob October 28th, 2019 10:11 pm
        Thank you for your response. Yes, figured out large downloads.
        Reply
    • Adel Mohebbi November 1st, 2019 1:53 pm
      OK.sure
      Reply
  • Ammar Sani October 23rd, 2019 4:57 pm
    Dear Ludo Waltman,
    I am new to this software. I've read your manual and all previous comments for looking to answer my confusing. But, I do not find any of them yet.
    I am now creating a co-occurrence map. There is an item named 'adaptive learning' which is connected only with my main keyword, 'learning analytics'. Once I hover on the item, it states cluster 1, links 40, total link strength 59 and occurrences 16.
    May I know why the links counted as 40 even though there is only one link, which is the one mentioned above?
    Thanks
    Reply
    • Ludo Waltman October 23rd, 2019 5:59 pm
      I think you need to increase the number of lines that are shown in the visualization. This can be done in the options panel in the right area of the VOSviewer window.
      Reply
      • Ammar Sani October 23rd, 2019 6:13 pm
        Thanks for this response. Yes that the solution. Now they are all showing perfectly! Thanks once again.
        Reply
  • Majid October 20th, 2019 12:00 am
    I recently downloaded the software from your website (OS=windows 10), and for some reasons, the information panel is missing. possible it is hidden? any chance I can bring it back?
    Reply
    • Ludo Waltman October 20th, 2019 8:23 am
      The information panel is available only for specific types of maps, in particular for citation-based maps of documents. In the case of a map of documents, the information panel is used to provide information about a selected document (e.g., title, authors, and publication year). For all types of maps, the status bar is available to provide general information about a map and about specific items in a map.
      Reply
  • Kahlil Lawless October 18th, 2019 9:17 pm
    I'm trying to load up a Dimensions data-set with >53,000 rows to do a co-authorship bibliometic analysis. The file is ~300MB. I keep getting OOM errors. Any estimate how much computing power I would actually need to perform this?
    Reply
    • Ludo Waltman October 18th, 2019 11:39 pm
      I am not sure how much memory you would need for this. However, you may try to remove redundant columns from your Dimensions CSV file. Most columns are not needed for a co-authorship analysis. Reducing the file size might make it easier for VOSviewer to process the file.
      Reply
  • Osaze Omoregbe October 18th, 2019 3:38 pm
    Hi guys,
    After using VOSViewer software for sometimes, I made a video to help beginners understand the use of the software. You can watch the video via the link: https://www.youtube.com/watch?v=EIKdq8mBllo
    Reply
    • Ludo Waltman October 18th, 2019 11:36 pm
      Thanks!
      Reply
  • Muhammad Ajmal Khan October 17th, 2019 8:01 am
    i tried to upload file containing around 8 thousands records with with references downloaded from Scopus but facing problem of "Out of memory" consult manual , that I consulted where is written run jar file there is no Jar file, I am using vosview1.6.13 for windows
    Muhammad Ajmal Khan
    Head, Library Quality and Academic Accreditation
    Liaison Librarian, College of Bussiness Administration and College of Public Health
    Deanship of Library Affairs
    Building A3 Central Library|New Campus
    Imam Abdulrahman Bin Faisal University, Dammam, KSA
    M: 00966 (0) 540783455
    T: 00966 (0) 13 33 32809
    Reply
    • Ludo Waltman October 17th, 2019 8:46 am
      The JAR file can be downloaded from https://www.vosviewer.com/download using the link 'Download VOSviewer 1.6.13 for other systems'.
      Reply
  • Juan Pablo Usuga October 16th, 2019 11:24 am
    Hello Mr. Waltman,
    Thank you for your last answer,
    I have another question:
    How does VOSviewer deal with keywords with missing year information to estimate the "average pub. year" in the Overlay visualization? Is VOSviewer ignoring these entries?
    Thank you,
    J.
    Reply
    • Ludo Waltman October 19th, 2019 10:24 pm
      What is the data source that you are using? And are you creating a keyword co-occurrence map or a term co-occurrence map (i.e., a co-occurrence map based on terms extracted from titles and abstracts)?
      Reply
      • Juan Pablo Usuga Cadavid October 21st, 2019 11:42 am
        Hello,
        I am creating a keyword co-occurrence map from the "Author keywords" (so no term extraction from abstracts).
        Thank you,
        J.
        Reply
        • Ludo Waltman October 21st, 2019 1:45 pm
          And what is the data source you are using?
          Reply
          • Juan Pablo Usuga Cadavid October 21st, 2019 2:07 pm
            Hello,
            I'm using a CSV file from SCOPUS (where I actually put also some references from ScienceDirect that I had to transform from a RIS file, as ScienceDirect is not directly supported by VOSViewer).
            Thanks,
            J.
            Reply
            • Ludo Waltman October 23rd, 2019 6:55 am
              We checked the VOSviewer source code. It turns out that in the case of a keyword co-occurrence map a missing publication year is treated as a publication year that is equal to -1. This is a bug. We will fix this in the next update of VOSviewer. Thank you for bringing this issue to our attention.
              By the way, when working with Scopus data, there normally should be no missing publication years in the data.
              Reply
  • stephanie October 11th, 2019 9:44 am
    Hi all, I have a couple of questions, one related to co-occurrences and the other to the country information.
    1- Is it correct to say that the co-occurrence map is 'only' using the keywords information ? It would be nice to create a co-occurrence map using title and abstract data as well, is this something I can do by creating a corpus myself? Has anyone tried it? Does that work 'well' or are there some issues?
    2- Is the 'country' information, for example in the bibliographic coupling feature, related to the organization country (and not the author nationality)? For example an article authored by an author working at Berkeley University would be assigned to the USA, even if the author is not american ?
    thx in advance
    Reply
    • Ludo Waltman October 11th, 2019 9:47 am
      1. No, this is not correct. VOSviewer supports two types of co-occurrence maps, one based on keywords and the other based on terms extracted from titles and abstracts of publications.
      2. Yes, this is correct.
      Reply
      • stephanie October 11th, 2019 9:53 am
        So in VOSViewer the first option for co-occurrence, 'All keywords', includes titles + abstracts + author keywords?
        thx again
        Reply
        • Ludo Waltman October 11th, 2019 4:53 pm
          No, this option is just for keywords, not for terms from titles and abstracts. My suggestion is to take a look at Section 3.5.4 in the VOSviewer manual. This should clarify things.
          Reply
  • Juan Pablo USUGA CADAVID October 7th, 2019 4:19 pm
    I have two questions concerning the relatedness and one concerning the clusters:
    1) Could you please explain me the difference between the lines and the spatial position of two words in the graph? In other words, do the lines and the spatial position (closeness) tell the same information? (strong line = close elements and weak line = far elements)
    2) Do you have any paper where I can find more details about the estimation of this relatedness with the lines. If so, could you please give me the reference to read it?
    3) Do you have any paper where I can find more details about the creation of clusters? If so, could you please give me the reference to read it?
    Thank you in advance,
    J.
    Reply
    • Ludo Waltman October 11th, 2019 9:13 am
      1) Correct. The lines and the closeness provide approximately the same information. The proximity of two items approximately reflects the strength of the link between the two items.
      2) We don't have a paper specifically on this topic.
      3) See https://doi.org/10.1016/j.joi.2010.07.002 or https://arxiv.org/abs/1006.1032.
      Reply
  • Lotus Ramana September 30th, 2019 4:21 pm
    I am using VOSviewer for text mining, and I’m having difficulty understanding how the Occurrences attribute is calculated. According to the VOSviewer manual, “In the case of full counting, the Occurrences attribute indicates the total number of occurrences of a term in all documents.” This seems simple enough, but when I create a visualization based on text data, using the full counting method, I get a map which shows a particular term with “Occurrences: 4,” and I am certain that in my corpus the term appears 15 times. Can you suggest any reasons for this discrepancy? Many thanks, in advance.
    Reply
    • Ludo Waltman October 5th, 2019 10:49 pm
      It is difficult to answer your question without seeing your data. If you send your data to vosviewer@cwts.leidenuniv.nl and if you explain which term you are referring to, I can take a closer look and I will try to answer your question.
      Reply
      • Lotus Ramana October 14th, 2019 1:49 pm
        Thanks so much for your response and for clearing this up for me!
        Reply
  • Aamir Memon September 27th, 2019 3:06 pm
    I am struggling to define the terms "link" and "link strength" in my paper. In the network visulation map for author keywords, we had 66 keywords with 479 links and a total link strength of 1338 (minimum link strength = 6, maximum link strength = 456). How do we define it in simple terms?
    Thanks in advance!
    Best,
    Aamir
    Reply
    • Ludo Waltman September 28th, 2019 1:35 pm
      Please see my response below to the question by David Sanchez. This question is similar to yours. Chapter 2 in the VOSviewer manual also explains this issue. Let me know if you need additional information.
      Reply
      • Aamir Memon September 29th, 2019 6:19 pm
        Dear Dr. Waltman,
        I had already seen the response to the question by David Sanchez and had read the description in chapter 2 as well. I would, however, be grateful to get your response to this particular situation that I discussed in my question because the description is still unclear to me.
        Thank you in advance!
        Best,
        Aamir
        Reply
        • Ludo Waltman September 29th, 2019 7:28 pm
          There are 479 pairs of keywords between which there is a co-occurrence link. Each link has a link strength, which is the number of documents in which two keywords co-occur. The sum of the link strengths equals 1338.
          Reply
          • Aamir Memon September 29th, 2019 9:31 pm
            This means that in 66 keywords included, there were 479 pairs of keywords between which there was a co-occurrence link. For example, physical activity and sleep co-occur together making a link of co-occurrence. Is this a correct explanation?
            Each link has a link strength, which is the number of documents in which two keywords co-occur. The group of keywords co-occurred in a way that that the sum of the link strengths was 1338. Is that right?
            Thanks for the explanation!
            Best,
            Aamir
            Reply
            • Ludo Waltman October 5th, 2019 10:55 pm
              Yes, correct!
              Reply
  • Deepa September 26th, 2019 1:27 pm
    Dear Dr. Ludo Waltman,
    Is there any way that I can import my edited Scopus CSV excel file into VOSViewer? Currently, it is not allowing me to choose among the types of analysis i.e., by default the software is only running the co-authorship analysis.
    Thanks.
    Reply
    • Ludo Waltman September 28th, 2019 1:25 pm
      Our advice is not to edit Scopus CSV files in MS Excel. Although in principle it is possible to edit Scopus CSV files, in practice this almost always causes all kinds of problems.
      Reply
      • Deepa September 28th, 2019 7:00 pm
        Okay.
        But sir, if we require to clean the Scopus data first (to yield accurate results), can we convert the file into an excel sheet, make the desired changes and reconvert the file into csv format, before importing into VOSViewer?
        Reply
        • Ludo Waltman September 28th, 2019 8:26 pm
          I am afraid this will cause problems. The difficulty is that a cell in Excel has a maximum size. Certain fields in a Scopus CSV file, such as the reference field, sometimes exceed the maximum size of a cell in Excel. This is causing problems.
          Reply
          • DEEPA September 29th, 2019 10:54 am
            Alright, sir. I'll search for better alternatives then.
            Thank you so much for your valuable suggestions.
            Reply
  • Varsha September 26th, 2019 1:13 am
    I cant able to open the file and the message shows
    "while reading VOSviewer thersaurus file (line:1): PTT is not a valid coloumn header)".
    Kindly help me
    Thanks ,
    Varsha
    Reply
    • Ludo Waltman September 28th, 2019 1:23 pm
      The only valid column headers for the first line of a thesaurus file are ‘label’ and ‘replace by’. See Section 4.3 in the VOSviewer manual for more details.
      Reply
  • Kumar September 22nd, 2019 7:15 pm
    Dear Ludo Waltman,
    Is it possible to know the source documents of keywords such that the relevant papers can be separated for literature review and analysis?
    Reply
    • Ludo Waltman September 22nd, 2019 10:30 pm
      There currently is no easy way to obtain this information in VOSviewer. However, there is an option that you could use. When creating a keyword co-occurrence map, in the final step of the 'Create Map' wizard, a table is shown listing the keywords to be included in the map. By right-clicking on this table, it is possible to export the document-keyword relations to a file.
      Reply
      • Kumar September 23rd, 2019 3:10 pm
        Dear Ludo Waltman,
        Thank you for your immediate response. I could use the method and get needful information. I have another query. I have downloaded search results from both Web of Science and Scopus. Is there a method to develop a single keyword map from both these results. Secondly, whether the duplicate items in both the results affect the output. Is there a way to eliminate duplicates.
        Reply
        • Ludo Waltman September 23rd, 2019 3:58 pm
          I am afraid there is no easy way to merge data obtained from different data sources.
          Reply
          • Leo Soares September 24th, 2019 3:13 pm
            Hi there. Ive seen a paper where He merged both collections into mendeley to eliminate duplicates. But Im not sure if it was to prepare the data for VOSViewer or another software.
            Reply
  • Lurdes September 16th, 2019 11:26 pm
    Dr. Ludo Waltman,
    It's possible to know the Degree, Betweenness Centrality and Closeness Centrality in the co-citation network (Cited references).
    Thanks
    Reply
    • Ludo Waltman September 17th, 2019 12:04 am
      VOSviewer does not provide centrality statistics. I personally believe they are often misinterpreted and used incorrectly. In VOSviewer, you can save your map in a GML file or in a Pajek network file. You can then perform centrality calculations in Gephi or Pajek.
      Reply
  • xin September 7th, 2019 1:13 am
    Dear Dr. Waltman,
    Just wondering is there any way to use zotero exported document and put them into VOSviewer?
    Otherwise, do you know any approach that I can export zotero data into scoupus or web of science bibliography format? I could not find a way so far, but I really do not want to mannully assmble 150 citations again in scoupus to visualize it...
    Thanks a lot!
    Reply
    • Ludo Waltman September 8th, 2019 11:25 am
      Do you have DOIs for your documents? In that case, my advice would be to export the DOIs in a plain text file, to provide this file as input to VOSviewer, and to then use the Crossref or COCI API to obtain bibliographic data for your documents. An alternative approach could be to try to export your data from Zotero in a RIS file. This RIS file can then be provided as input to VOSviewer. Exporting your data in a file in the Web of Science or Scopus file format won't be possible.
      Reply
      • xin September 8th, 2019 8:37 pm
        Hi Dr.Waltman,
        I tried to export the RIS data from Zotero and imported it to VOSviewer. It really helps!!!
        Thanks!
        Best,
        Xin
        Reply
  • Ibtissam Zaza September 6th, 2019 11:50 pm
    Dear Dr. Waltman,
    I am new to VOSviewer. I am trying to create a map based on bibliographic data. I chose that option -> read data from reference manager files -> select files "EndNote". My question, if my library is in EndNote X9, how can I download a file with the extension .enw from EndNote? If you can direct me, I highly appreciate it!
    Reply
    • Ludo Waltman September 8th, 2019 11:28 am
      I am afraid I cannot help with this. I am not an EndNote user myself, so I cannot provide any guidance on how to use EndNote.
      Reply
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