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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  • 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
  • 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
  • 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
  • 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
  • Omwoyo Bosire Onyancha June 26th, 2020 9:02 pm
    Hi all,
    Please assist me here. Does anyone know why some of 'types of analysis' on VOSViewer, i.e. citation, bibliographic coupling. and co-citation analysis, are inactive (deactivated). I am trying to conduct a citation analysis of journals using Scopus data saved as .csv format.
    Regards
    Reply
    • Ludo Waltman June 26th, 2020 9:50 pm
      When exporting Scopus data to a CSV file, you need to make sure to include reference information. This will solve your problem.
      Reply
      • Bosire June 28th, 2020 7:25 pm
        Thanks Ludo for your reply. I will try again and see what happens.
        Regards
        Bosire
        Reply
      • Bosire June 28th, 2020 10:26 pm
        It worked, Thanks.
        Reply
  • Dan June 21st, 2020 3:26 pm
    Hello,
    I am doing a co-citation analysis at the document level.
    When the Link strength between Article A and Article B is 20.
    Does this mean that Article A and Article B were cited 20 times together by the references of the articles contained in my data set?
    The total strength of Article A is 320. Does this mean that Article A was co-cited in my data set 320 times?
    Reply
    • Ludo Waltman June 21st, 2020 5:08 pm
      Yes, both are correct!
      Reply
  • Frieyadie June 19th, 2020 6:36 pm
    I have a problem. Want to ask, why when Create Map Type analysis Co-Occurance is not active / Disable huh?
    What is the solution?
    Thanks
    Reply
    • Ludo Waltman June 19th, 2020 10:41 pm
      If your input data doesn't include keywords, VOSviewer disables the option for creating a keyword co-occurrence map.
      Reply
      • rosy June 21st, 2020 8:27 am
        I also have the same problem, I already downloaded from PoP with keyword and save the result as RIS, however when a choose create a map with bibliographic data, the co-occurrence fitur was disabled. Could you give me advise about that (VosViewer 1.6.15). Thanks
        Reply
        • Ludo Waltman June 21st, 2020 9:13 am
          Your RIS file apparently doesn't include keywords, so it's then impossible for VOSviewer to create a keyword co-occurrence map. If you want to create such a map, you need to use a data source that does provide keywords (e.g., Web of Science, Scopus, or PubMed).
          Reply
          • rosy June 22nd, 2020 5:38 am
            Thank you Ludo
            Reply
  • giuseppe vito June 19th, 2020 10:05 am
    combining the database from WoS and Scopus:
    see in this blog Giuseppe Vito apr. 9, Ludo Waltman apr. 19, Giuseppe Vito apr. 22.
    Greetings
    Reply
  • Hamdan June 19th, 2020 8:34 am
    Hi,
    If I have an item (publication A) that has: 8 links, the total strength of the links is 15 and citations are 410.
    Does this mean that publication A is cited along with 8 different publications?
    The Link Strength between publication A and publication B is 3.
    Does this mean that publication A and publication B were cited three times in one article or in several articles at the same time?
    Citations 410: Does this mean that publication A was cited 410 times?
    There is a big difference between the number of Citations 410 and the total link strength. What is a possible explanation for this?
    Best regards,
    Hamdan
    Reply
    • Ludo Waltman June 19th, 2020 10:32 pm
      Could you explain what kind of map you have created (e.g., citation, bibliographic coupling, or co-citation)? The number of citations (410) is the total number of citations a publication has received in the database you are using (e.g., Web of Science, Scopus, or Dimensions). So it is not the number of citations received in your data set, but the number of citations received in the entire database. Other statistics, such as the number of links and the total link strength, are based on your data set, not on the entire database.
      Reply
      • Hamdan June 20th, 2020 12:58 am
        Thank you for your quick response.
        I am doing bibliographic coupling.
        and how can we explain the mentioned information in the case of co-citation?
        Reply
  • Koushik Sau June 18th, 2020 12:48 pm
    dear sir if I want to export more than 2000 documents for my field it only provides citation documents then how can I can study which keywords using more in my field. full document export if contain less than 2000 documents
    Reply
    • Ludo Waltman June 19th, 2020 10:14 pm
      I assume you are using Scopus data? You then need to find a way to split your data into batches of no more than 2000 documents each. Perhaps you can do this by creating a separate batch for each publication year.
      Reply
  • ReyaAk June 14th, 2020 6:53 pm
    Is there any possibility that we can combine the database from WoS and Scopus? And analyse it using VOS?
    Reply
    • Ludo Waltman June 15th, 2020 4:11 pm
      Unfortunately this is not possible. There are important differences between the two databases in the file formats they support.
      Reply
  • Manuel June 14th, 2020 8:51 am
    Thank you for this useful tool. I cannot download the Windows version from the Download page. In most cases the download doesn't start ("500 - Internal server error."); if it does, it stops always after downloading 4mb. Is there any alternative, external hosting for this file available?
    Reply
    • Ludo Waltman June 15th, 2020 4:06 pm
      Thanks for reporting this problem. The problem has now been fixed.
      Reply
  • Yeri June 13th, 2020 2:43 pm
    Hello,
    Thank you for your useful tool. I've got one question.
    I used web of science record data for network visualization.
    What I would like to get is the adjacency matrix (diagonal matrix) from this map.
    Could you please kindly let me know how I can get that data?
    Like "journal_network_full.txt" in data folder.
    Best regards,
    Yeri
    Reply
    • Ludo Waltman June 14th, 2020 7:55 am
      The adjacency matrix can be obtained by saving the network underlying your map in a VOSviewer network file. This can be done using the 'Save' button on the 'File' tab. The network file will have a so-called sparse format, which means that only the non-zero entries of the adjacency matrix are stored in the file.
      Reply
  • Ghaliamus June 9th, 2020 6:37 pm
    Hello,
    I thank you so much for your great efforts behind this great software. I have one question please.
    You used PCA in the transformation step (the third step) for the solution (the presented map). What I know about PCA is that the distance between points in the first component (x-axis) dimensions are more important than the distance between points in the second component (y-axis). However, you used more than PCA in your transformation step.
    Now, can I assume that the importance of distances in the VOSviewer maps is the same in both vertical and horizontal perspectives? And therefore, there is no need to care about x-axis and y-axis in describing the produced map?
    Best wishes,
    Ghaliamus
    Reply
    • Ludo Waltman June 9th, 2020 11:04 pm
      The horizontal and vertical axes have no special meaning in a VOSviewer map. What matters are the distances between the items. You may rotate a map and this shouldn't change your interpretation of the map, since the distances between the items remain the same.
      Reply
      • Ghaliamus June 28th, 2020 5:26 pm
        I thank you so much for your response. If I can ask, if axes have no meaning, and if we have item A and item B with the same distance with item C, why we can have item A above item C (in vertical distance) and item B next item C (in horizontal distance), I could understand how VOS find the distance, but how it located such items, I could not get it. I am sorry if I am missing an obvious point here.
        Reply
        • Ludo Waltman June 28th, 2020 7:50 pm
          I am not sure if I understand your question. The details of the VOS layout technique can be found in the following paper: https://doi.org/10.1002/asi.21421 (and also in the book chapter mentioned at the top of this page). As already mentioned, a map can be freely rotated. This doesn't change the interpretation of the map. By default, VOSviewer uses principal component analysis to rotate a map in such a way that the variance in the horizontal dimension is maximized.
          Reply
  • AYNU June 9th, 2020 2:13 am
    Thanks for your continuous support. I have following questions.
    1. Citations, then unit of analysis "country"; then does it show the origins of articles of documents where authors were working?
    2. How to get the "sources of primary data by country" using VOSviewer? or we have to find by reading all articles in the dataset?
    Reply
    • Ludo Waltman June 9th, 2020 11:00 pm
      1. Country means the country mentioned in the affiliations that authors report in their publications.
      2. I am not sure what you mean by 'sources of primary data by country'.
      Reply
      • MD AYNUL HOQUE June 11th, 2020 6:58 am
        Thank you for your kind support. "sources of primary data by country" : For example, an author published an article who is working at Harvard University which is his affiliation but he used data from Malaysia. So the source of data was Malaysia and his affiliation was Harvard. I wanna know how to find source of data using VOSviewer? or is there any other software for this purpose?
        Reply
        • Ludo Waltman June 12th, 2020 11:58 pm
          Thanks for clarifying your question. VOSviewer is unable to determine the source of the data. I am not familiar with any tool that it able to determine this.
          Reply
  • Omwoyo Bosire Onyancha June 3rd, 2020 5:44 pm
    Does anyone know how to analyse data that is in Excel Spreadsheet? I have downloaded data from Google Scholar, using publish or perish software. How can I analyse the data using VOSviewer?
    Reply
    • Ludo Waltman June 3rd, 2020 7:42 pm
      VOSviewer requires your data to be in a well-defined format. Just having your data in an Excel spreadsheet is not enough. In your case, my advice is to use Publish or Perish to save data from Google Scholar in a RIS file. This RIS file can then be provided as input to VOSviewer. However, as you will see, the possibilities offered by VOSviewer when a RIS file is provided as input are limited.
      Reply
  • Mike June 2nd, 2020 3:20 am
    Hi
    Thank you for your great software. I have a quick question. I am plotting the co-authorship network using data from Web of Science. Is there any way I can capitalize the first letter of the family names?
    Reply
    • Ludo Waltman June 2nd, 2020 12:34 pm
      This can be done by saving your map in a map file and by manually editing this file in a spreadsheet program such as MS Excel. In the 'label' column, you can capitalize the first letter of the name of each author.
      Reply
      • Mike June 3rd, 2020 9:33 pm
        Thanks very much Ludo. I will give it a try.
        Reply
  • Camille June 1st, 2020 11:50 pm
    Hi, I am trying to create a co-citation map but when I get to "choose type of analysis and counting method", the only options I can choose are "co-authorship" for the type of analysis and "authors" for the unit of analysis. Could you please explain me how I can "unlock" the other options?
    Reply
    • Ludo Waltman June 2nd, 2020 12:48 pm
      The options made available by VOSviewer are determined by the data that you provide as input to the software. Depending on the limitations of the data, certain options will not be made available. If you want to be able to make use of all options, my recommendation is to use a data source such as Web of Science, Scopus, Dimensions, or Microsoft Academic.
      Reply
      • Camille June 4th, 2020 5:04 pm
        Thank you for your answer ! I already use the data source Web of Science and it doesn't work... By "the data you provide as input to the software" you mean the key words I enter in the first place in the search engine?
        Reply
        • Ludo Waltman June 4th, 2020 6:33 pm
          When exporting data from Web of Science, make sure to follow the instructions on p. 27 in the VOSviewer manual. This should solve your problem.
          Reply
  • MD AYNUL HOQUE May 30th, 2020 10:02 pm
    Dear Sir,
    1. How many documents or articles are minimum standard for conducting bibliometric analysis for writing academic articles ? please give me the reference.
    2. How to give reference of Vosviewer version 1.6.3 in academic articles?
    Reply
    • Ludo Waltman May 30th, 2020 11:32 pm
      1. There is no clear minimum for the number of documents. When you have just a few documents, a VOSviewer visualization usually has little or no value and it is more informative to read the documents. In general, the larger the number of documents, the more value you will get from a VOSviewer visualization. Typically visualizations start to become useful when you have at least a few hundred documents, but this also depends on the type of visualization that you are interested in.
      2. You could cite the following paper: https://doi.org/10.1007/s11192-009-0146-3.
      Reply
      • MD AYNUL HOQUE June 2nd, 2020 12:43 pm
        Is it possible to use when we have about one hundred documents?
        Reply
        • Ludo Waltman June 2nd, 2020 2:16 pm
          Yes, as I said, there is no clear minimum. In the end, you need to decide yourself whether or not you find a visualization helpful and whether or not a visualization provides insights that you couldn't easily obtain in an alternative way (e.g., by skimming a set of documents).
          Reply
  • Roja May 29th, 2020 1:40 pm
    Thank you for the great app
    How can I access the "thesaurus" example file?
    Reply
    • Ludo Waltman May 30th, 2020 8:06 am
      The example files are included in the ZIP files that you can download from https://www.vosviewer.com/download.
      Reply
  • Camille Lassalle May 29th, 2020 1:57 am
    Good evening, I would like to know if the analysis we can conduct via VOSviewer differs regarding the origin of the files.
    When downloading files directly from Web Of Science to VOSviewer I am able to conduct all kind of analysis.
    However , when I import files from Web Of Science to Endnote ( selecting full records + citations) and then from Endnote to VOSviewer I don't have access to all kind of analysis.
    I used Endnote to clean the data and keep the more relevant articles for the analysis.
    Any ideas of why I can't access to all kind of analysis with files coming from Endnote ?
    Thank you really much in advance.
    Best,
    Camille
    Reply
    • Ludo Waltman May 29th, 2020 7:06 am
      The features available in VOSviewer are indeed dependent on the types of files that you provide as input. Files from Web of Science include a lot of valuable information, and they therefore enable VOSviewer to offer many different features. Files from EndNote, on the other hand, contain less information, and therefore VOSviewer is unable to offer certain features. In particular, it is not possible to create citation-based maps based on EndNote files, since the data required for creating such maps is not available in these files.
      Reply
  • Christian Daniel Moreno Avendaño May 28th, 2020 7:25 pm
    Buenos dias, tengo un problema para realizar la instalacion de VOSviwer, al descargar el paquete me pide tener Java Rutime Environment 1.8.0, mi computados tiene problemas para descargar Java, quisisera saber de que forma puedo descargar Vosviwer sin descargar Java.
    Muchas gracias por su atención y colaboración.
    Reply
  • Ayaz Khan May 21st, 2020 2:37 am
    how can we calculate normalized citation and average normalized citation and what is the significance of this?
    Reply
    • Ludo Waltman May 21st, 2020 7:23 pm
      Please see p. 37 in the VOSviewer manual.
      Reply
  • Mia Be May 20th, 2020 8:00 pm
    I have 1,271 articles and when I go to choose the type of analysis only co-authorship and co-occurrence options are possible.
    AND
    When I choose co-occurrence an error message pops out "Insufficient number of keywords. There must be at least three keywords".
    Help please and thx
    Reply
    • Ludo Waltman May 20th, 2020 8:06 pm
      Perhaps there are no or almost no keywords in your data. Could you tell more about the type of data you are working with? What is the data source?
      Reply
  • Kai May 20th, 2020 11:54 am
    My computer environment is: masOS Mojave. My vosviewer has been running without any problems before. Recently, clicking and finishing will cause a flashback. This is the case every time. This crash phenomenon can also be caused by a small amount of data, and java environment everything is normal. What should I do? Please help.
    Reply
    • Ludo Waltman May 20th, 2020 8:03 pm
      Sorry to hear about this problem. You seem to be the first one reporting this issue. I don't have an immediate solution. If others experience the same problem, I would be interested to know.
      Reply
    • Nicole June 17th, 2020 2:59 pm
      I met the exactly same issue! Have you figure out a solution? I tried reinstall, restart Mac, reinstall Java, but all failed to make the vosviewer work again...
      Reply
  • James Hill May 19th, 2020 1:59 pm
    Is there a way to open the map file .txt In Excel which would allow editing of the individual outputs. I know when I opened it in Excel it currently puts all the information into a single column is there anyway to separate it out into individual columns?
    Reply
    • Ludo Waltman May 20th, 2020 7:49 pm
      It should be possible to fix this by using the 'Text to Columns' feature in Excel (in the 'Data' menu).
      Reply
      • James Hill May 22nd, 2020 11:26 am
        Thank you so much!!! you saved me many hours of work.
        Reply
  • Boryana Georgieva May 19th, 2020 1:43 pm
    I am missing the .jar file after I download it from vosviewer.com/download for Windows. I need the .jar file to take a network from Rstudio into vosviewer. How can I get the file? Am I doing something wrong?
    Reply
    • Ludo Waltman May 20th, 2020 7:38 pm
      You need to use the link 'Download VOSviewer 1.6.15 for other systems'. This will give you the JAR file.
      Reply
  • Anirudh Badarinath May 15th, 2020 2:12 pm
    Hi!
    Is there a way that I can exclude certain keywords from the co-occurance map (if they're remote and very scantily connected) using the thesaurus file?
    Thanks!
    Reply
    • Ludo Waltman May 15th, 2020 8:13 pm
      Yes, this is possible, simply by leaving the 'replace by' column in the thesaurus file empty.
      Reply
  • Nawaid ALAM May 14th, 2020 9:57 am
    I am a bit confused. With a total of 78 papers, I am conducting Co-citation analysis at the author level. Link Strength between Author A and Author B is 310. Does it mean that Author A and B were co-cited 310 times in the references of included papers? If not, then what should be the interpretation of this link strength value between two authors.
    Thanks in advance
    Reply
    • Ludo Waltman May 14th, 2020 8:02 pm
      Yes, A and B were co-cited 310 times. Why are you confused? Please note that one paper may result in multiple co-citations of A and B. For instance, if A is cited 2 times in a paper and B is cited 3 times in the same paper, this yields 2 x 3 = 6 co-citations of A and B.
      Reply
      • Nawaid ALAM May 14th, 2020 8:59 pm
        Perfect, I am clear now. Thank you
        Reply
  • PJH May 14th, 2020 3:54 am
    Hi
    I am using the temporal overlay on a keyword map and would like to affirm if my understanding is correct.
    I think that for each keyword VOSviewer identifies the distribution of publication years for documents associated with the keyword. Then an algorithm is used to identify when the keyword has been most popular.
    What is the algorithm? For example, do you use the mean, median or another formula to determine the time period and color associated with a keyword?
    Thanks.
    Philip
    Reply
    • Ludo Waltman May 14th, 2020 8:37 am
      We use the mean, so the color of a keyword represents the average publication year of the publications in which the keyword occurs.
      Reply
  • Lorena Rojas May 14th, 2020 1:18 am
    Hi, I love Vosviewer but I want to clean the data that I import first, and the easy tool that I have to do that is Excel ( I don't know how to program :( ), so I want to know if I can somehow import excel data to Vosviewer or If you recommend any free tool for cleaning data. Thanks :)
    Reply
    • Ludo Waltman May 14th, 2020 8:34 am
      What is the source of your data?
      Reply
      • Lorena May 15th, 2020 8:18 pm
        I use different sources, for example, I downloaded bibliographic data of our library OPAC (Sirsy Simphony), to analysis thesis and dissertations to know the most researched topics. Or sometimes I mix information of different databases or sources from grey literature, to do a state of art
        Reply
        • Ludo Waltman May 15th, 2020 8:23 pm
          Thanks for this information. Could you also let me know the file format that you use to provide your data as input to VOSviewer?
          Reply
          • Lorena May 20th, 2020 8:10 pm
            It downloads as .txt delimited by a vertical bar (|)
            Reply
  • Andy Yeung May 12th, 2020 4:37 am
    I would like to ask whether it is possible to check discipline-retained citation ratio. For example, if Paper A belongs to neuroscience (WoS category or Scopus subject area), how many times it is cited by neuroscience papers and non-neuroscience papers?
    Method 1: From WoS / Scopus, I can generate a list of papers citing Paper A, and then check the category / subject area distribution of these citing papers. This should work for a single paper (e.g. Paper A) but do not work for a collection of papers (e.g. if I want to check a collection of Papers A to E). Because a neuroscience paper can contribute to multiple cites, such as cites to all Papers A to E. By this method, 5 citations will show as a single citing paper in the output.
    Can VOSviewer or other solutions help? Would be great to have your recommendations on this. Thank you very much for your time.
    Best regards, Andy
    Reply
    • Ludo Waltman May 12th, 2020 10:11 pm
      It seems to me that this requires API access to a bibliographic database (e.g., Scopus, Dimensions, or Microsoft Academic) combined with some custom programming. I don't think VOSviewer is the right tool for this.
      Reply
  • James Hill May 9th, 2020 10:29 am
    Just wondering if you can help me I am using vosviewer as part of a systematic review around domestic violence. When I separate the citations for a map based on text data into yearly sections 5 years the term partner violence is highly prevalent throughout the data set. With over 807 occurrences out of 2288 citations. However when I add all the citations together and carry out the same analysis the term does not even appear and the number of the individual terms be mentioned separately is not near the 807. Just wondering why this may be occurring as we were planning to do the separate five year analysis and the combined data set analysis? It is difficult to explain why a term can be so highly prevalent throughout the data set was then not appear when you combine them.
    Kind regards James
    Reply
    • Ludo Waltman May 9th, 2020 4:26 pm
      This seems to be caused by the fact that, by default, VOSviewer removes the 40% least relevant terms from the analysis. Relevancy is determined by a text mining algorithm. The algorithm assigns a low relevance to terms that have little value in describing the organization of the literature provided as input to VOSviewer. My guess is that the relevance of the term 'partner violence' is relatively low because the term does not specifically describe one topic within the literature but instead offers a description of the entire body of literature provided as input to VOSviewer. The term 'partner violence' may therefore be a borderline case. In some cases, it may belong to the 60% most relevant terms. In other cases, it may belong to the 40% least relevant terms. I think you should decide yourself whether you want this term to be included in your analysis or not. It is always possible to overrule the default choices in the 'Create Map' wizard to ensure that a particular term is either included in or excluded from the analysis.
      Reply
      • James Hill May 9th, 2020 4:58 pm
        I would first like to say thank you for your reply is a much appreciated your quick response and support with this software.
        It would be important that this term is included . I was thinking along the same lines I tried increasing the threshold to include all terms instead of the standard 60%. The term did appear when I did this but it still had a relatively low occurrence count compared to the individual five year period. I also tried all the other settings in regards to binary counting full counting abstract only et cetera see if it had a similar pattern and it did. Just wondering if you could help me with the command to make sure it counts this time for the combined library. Just that I'm doing this analysis for a research team and it can going to struggle to explain why the term is so prevalent in the five year periods and then when I combine the citations it disappears. Do you know why the occurrence count would be so much lower than the five year periods in both binary and full counting in the combined library compared to the 5 Years Libraries. I would assume when I combine it is not identifying all the occurrences of that term to be important not counting every one of them as it does in the five year period versions. We were planning to make a table which would count the occurrence of the term in each five year period with the idea that it should add up to the same as combined library with all years?
        Reply
        • Ludo Waltman May 9th, 2020 6:33 pm
          When you combine data from multiple time periods, the occurrence counts for the combined data should not be lower than those for the individual time periods. Could you send your files to vosviewer@cwts.leidenuniv.nl? I will then try to reproduce your problem and to offer advice.
          Reply
          • James Hill May 9th, 2020 9:17 pm
            I have sent you the files for you with a bit of a description of the problems if you need any more information or anything about the original endnote file et cetera please not hesitate to ask.
            Kind regards James
            Reply
  • Daniel May 8th, 2020 6:57 pm
    Not directly related to VosViewer software, but is there a way to export bibliometric metadata of more than 500 references at once in WoS?
    Reply
    • Ludo Waltman May 9th, 2020 9:08 am
      I believe the Web of Science web interface doesn't provide a way to export data for more than 500 records. There is a 'Fast 5K' export option, but this option exports only a limited number of data fields.
      Reply
  • nidhi May 4th, 2020 5:18 pm
    How can I get to know about the most productive author by using VOSviewer?
    Reply
    • Ludo Waltman May 4th, 2020 7:24 pm
      VOSviewer is intended for bibliometric network analysis, not for ranking authors. However, when you create a map of a co-authorship network, the size of an author reflects the number of publications of the author, so in this way it is possible to identify the most productive authors.
      Reply
      • Nidhi May 6th, 2020 7:28 am
        Sir

        WoS is showing different most productive author and VOSviewer is showing different. How to justify most productive author in publication.
        Reply
        • Ludo Waltman May 6th, 2020 7:45 am
          I am afraid I cannot help with this very general question. There are multiple ways in which the concept of productivity can be operationalized bibliometrically. You need to choose yourself which approach is most suitable for the purpose of your analysis. The most important thing is to explain why you make a certain choice and to explain the pros and cons of this choice.
          Reply
  • Emily Lee May 1st, 2020 11:07 am
    when i tried to open map, and has finished selecting VOSviewer map file and VOSviewer map file, but it showed error notification,and about 15 seconds later, VOSviewer quit suddenly.
    Reply
    • Ludo Waltman May 2nd, 2020 11:17 pm
      Could you send the map file to vosviewer@cwts.leidenuniv.nl? I will then take a look at your problem. Thanks.
      Reply
  • Anirudh May 1st, 2020 6:29 am
    Hi,
    Thanks for a wonderful tool btw! It's absolutely fantastic.
    I have followed all steps as laid out while exporting from Web of Science. However, when I select 'Create map based on network data' and pick the .txt file (exported from WoS), I get an error message 'incorrect use of quotes'. Any particular reason?
    Can I receive any help?
    Reply
    • Ludo Waltman May 1st, 2020 8:38 am
      When working with Web of Science data, in the first step of the 'Create Map' wizard you should use either the option 'Create a map based on bibliographic data' or the option 'Create a map based on text data'.
      Reply
  • Giuseppe Vito April 22nd, 2020 10:25 am
    Vos Viewer - End Note
    Dear Ludo,
    The answer you gave on April 19th is perfectly correct. However, there are conversations in this blog that explain in detail the procedure for exporting from EndNote. I use EndNote X7 and never find any problem.
    Greetings
    Reply
  • Ahmed Rashed April 22nd, 2020 3:17 am
    OK I'm sorry can u please briefly explain if I have an end note library how i can get the essential data and how to export it from end note what extension and how to import it to VOS viewer to get the authorship map since I'm having a serious difficulty figuring this out
    Reply
    • Ludo Waltman April 22nd, 2020 8:27 am
      I hope there are EndNote users on this forum that are able to provide such an explanation. Unfortunately, since I am not an EndNote user myself, I am unable to offer an explanation.
      Reply
  • Rafael Oliveira April 19th, 2020 9:03 pm
    Dear Ludo,
    I am very enthusiastic about your software tools. And I hope that you do not mind my asking three related questions regarding their differences.
    - Why would VOSviewer and CitNetExplorer yield different cluster solutions for a citation analysis (given the same dataset, the same resolution and optimization parameters and without including non-matching cited references)?
    - Are there differences between the clustering techniques employed by VOSviewer and CitNetExplorer ?
    - Does the former employ the Leiden Algorithm?
    Thank you in advance
    Rafael
    Reply
    • Ludo Waltman April 20th, 2020 11:59 pm
      VOSviewer and CitNetExplorer indeed use the same clustering technique. However, VOSviewer uses a more recent version of the optimization algorithm. VOSviewer uses a variant of the Leiden algorithm, while CitNetExplorer uses an older algorithm. In practice, this shouldn't make a big difference. To obtain similar clustering solutions in the two software tools, it is important to use the 'Fractionalization' normalization method in VOSviewer (see the 'Analysis' tab). Importantly, the resolution values in the two tools do not have the same scale, so a resolution of, say, 0.5 in VOSviewer is not the same as a resolution of 0.5 in CitNetExplorer.
      Reply
  • Rhonda Buskell April 19th, 2020 5:54 am
    Hi, and thank you very much for this software and your time to give any advice. How is lockdown for you in the Netherlands? it seems to be working for us here in Australia at present.
    I'm just using VOSViewer for the first time, and trying to import my bibliographic data from my endnote library. I'm on a Mac, and my EN file names end in .enlx or .enl or .enlp . I've tried all, and either I'm told the file is empty (which I know it is not) or there is an error and, like the previous poster, 'can't find author(%A) or keyword (%K) field'. Can you advise me, please? Thanks, Rhonda
    Reply
    • Ludo Waltman April 19th, 2020 8:14 am
      Different versions of EndNote seems to use different file formats. VOSviewer supports only the ENW file format. I am afraid other EndNote file formats are not supported by VOSviewer. Perhaps you could use the RIS file format as an alternative?
      Reply
      • Rhonda Buskell April 19th, 2020 11:01 am
        Thank you, Ludo, I'll give that a try.
        Rhonda
        Reply
  • Ahmed Rashed April 18th, 2020 6:12 am
    hey, and thanks for such a great software
    I'm trying to conduct a co-authorship map, i have files from endnote since i used 2 different data base web of science and science direct, i export the data to txt type then i open the data in note pad and changed the extension to all files and enw extension went to VOS and i was trying the bibliographic data then data from end note then i had this error stating error while reading end note file : can't find author (%A) or keyword (%K) field
    can you please tell what I'm messing here
    thanks in advance
    Reply
    • Ludo Waltman April 19th, 2020 12:13 am
      Your question is not entirely clear to me. I don't understand why you have manually changed the extension of your file to ENW. The error message indicates that your file is not a valid ENW file. To obtain a valid ENW file, the file should be exported directly from EndNote without making any further manual changes to the file.
      Reply
  • shiza shamin April 13th, 2020 12:10 pm
    Dear Ludo Waltman,
    I just make choice of co-authorship and authors,but all other options are locked.i am using scopus data in .csv file.Can you help me to resolve this problem?
    Thanks in advance!
    Reply
    • Ludo Waltman April 13th, 2020 5:59 pm
      When exporting data from Scopus, you need to make sure to include all available information, in particular information on references. This will enable you to create other types of maps in VOSviewer, in addition to co-authorship maps.
      Reply
  • PJH April 9th, 2020 10:01 am
    Ludo
    Quick question. When conducting journal co-citation analysis is it more correct to refer to the results as "citations" or "co-citations"? For example,
    a. "The Journal of Educational Psychology accrued 2,325 co-citations in the reference lists of the review documents." Or
    b. "The Journal of Educational Psychology accrued 2,325 citations in the reference lists of the review documents." or
    c. both are correct
    Thanks.
    Philip
    Reply
    • Ludo Waltman April 9th, 2020 10:24 am
      VOSviewer in fact provides both statistics. They are available in the 'Weights' drop-down menu. 'Total link strength' is the total number of co-citations of a journal. 'Citations' is the number of citations of a journal.
      Reply
      • PJH April 9th, 2020 10:37 am
        Got it, thanks.
        Philip
        Reply
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