In MaximeRivest/scimeetr: Scientometrics Meet R

Introduction

Scimeetr helps explore the scholarly literature. It contains a suit of function that let someone:

• load bibliometric data into R
• make a map of peer reviewed papers by creating various networks
• find research community
• characterise the research communities
• generate reading list

This tutorial is composed of two self-contained section. The first section show case the whole process with all the default parameters. The second section describes each function in more detail by presenting the rational for the function, the algorithms used and the options.

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From data to reading list

You can automatically generate a reading list of seminal papers in a research litterature by using only those three functions: ìmport_wos_files, scimap, and scilist. This first section describes this process in more details.

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loading and exploring bibliometric data

The first step in exploring the literature is to retrieve bibliometric data from the Web of Science or Scopus. In this first tutorial I use a dataset from the Web of Science about ecological networks.

library(scimeetr)

library(scimeetr)
scimeetr_list <- import_wos_files("path/to/folder/")

Then,summary can be used to get a quick characterisation of the data.

summary(scimeetr_list)

From this summary, we see that there is 396 papers in my data set which overal cites 16567 different elements. On average, each paper cites 53 elements.

Than we learn that, in this research community, 25% of the papers are cited less than 2 times, 50% are cited less than 9 times and 75% are cited less than ~23 times. There are papers that are cited up to 1333 times. The average citation per paper is ~25. This is much higher than the median (9), thus most paper are cited only a few times and a few papers are profusely cited. When correcting for the age of the paper, we learn that papers are cited 2 times per year on average.

By looking at the most frequent keyword and journals, we learn that this community of research is about biodiversity, agriculture, ecosystem services and policy. Keyword and journal frequency tables efficiently reveal the theme of a scientific community.

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Mapping scientific community

The previous characterisation is great, but it is limited if your dataset contains many different scientific communities. By detecting the scientific communities present within a dataset a map of science can be drawn and each cluster can be characterised on its own. The function scimap can be used for this task.

scimap_result <- scimap(scimeetr_list)

The function returns all the data that scimeetr_list contained and more. For example communities have been identified and now if the function summary is used on scim_result. In addition of the previous information. The descriminant keywords of each communities constituating the main community are listed.

summary(scimap_result)

Except for the last tables, all of the output is identical to the summary output above. Those last tables now reveals that the papers in our database can be clustered in two communities. One that is about x and the other that is about y.

The function plot can be used on the output of the function summary for a graphical representation of the sub-communities.

plot(summary(scimap_result, com_size = 30))

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Automatically generating a reading list of seminal papers

Now that we have characterise the main community and seen of which community it is constituted, we can decide if it is the community that we wish to join / review. If it is, we use the function scilist to get reading lists. The defaul readin list will find the seminal papers of each communitiy.

reading_list <- scilist(scimap_result)
reading_list$com1

reading_list <- scilist(scimap_result)
knitr::kable(reading_list$com1)

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In depth description of each steps

How to get bibliometric data?

Biliometric data can be obtained from either Scopus or the Web of Science. Most university library have access to either one and some have access to both.

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Retrieving data from Scopus

Scopus home page.

Select all and export

Export as CSV file and select all fields for exportation

Following the previous steps will get you one or several .csv files. Then, to import this/these file(s) in R, you need to put it/them in a new folder which contains only the files to import into R

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Retrieving data from Web of Science

Web of Science home page. Make sure that Select a database corresponds to Web of Science Core Collection

Save to Other Files Formats

You can download only 500 items at a time. You should select Full Record and Cited References. And select the Tab-delimeted (UTF-8) as file format.

Following the previous steps will get you one or several .txt files. Then, to import this/these file(s) in R, you need to put it/them in a new folder which contains only the files to import into R

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How to upload bibliometric data into R

The bibliometric data obtained from Scopus or Web of science are either in .csv or .txt format. These are standard file formats and you most likely know them. There are built in function in R that let you import .csv and .txt files. So why does scimeetr provide you with import_scopus_files and import_wos_files? There are four reasons. The main one is that bibliometric data contains author names from around the world, which means that all alphabets are used and this leads to problems with file encoding. Scimeetr's import functions solves that problem. Second, Scopus do not provide standard, uniform and consisten cited reference list. Thus, import_scopus_files has to standardize it at import. This explains the additional time required to load scopus files versus wos files. Third, Scopus and Web of Science do not use the same column names so they have to be homogenized at import. Finally, the data can be transformed into a scimeetr object so that summary, plot and print will know what to do with it.

scimeetr_list <- import_wos_files(files_directory = "/path/to/folder/")
scimeetr_list <- import_scopus_files(files_directory = "/path/to/folder/")

Do not forget that this function take in a path to a folder not a file. Thus, it need a slash at the end of the folder path.

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Exploring scimeetr data

Printing scimeetr_list that we just created will provide some informations about it, but summary will provide more.

scimeetr_list
summary(scimeetr_list)

A scimeetr object such as scimeetr_list contains more data than what can be seen with print and summary. A scimeetr object is in fact a list of communities list which are themselves list of up to 9 elements. Each communities contain a data.frame called dfsci. This dataframe contains all the bibliometric data that was importedinto R.

scimeetr_list$com1$dfsci

knitr::kable(subset(scimeetr_list$com1$dfsci[1,],select = c(-AB, -CR, -FX)), format = "markdown")

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Making reading lists

If we are confident that the papers contained in scimeetr_list are those for which we want a reading list we can used the function scilist to find various lists of papers. The default list given by scilist contains the seminal papers for the community analysed. That is, it rank the paper by the number of times they were cited by all the papers and list them by citation frequency.

scilist(scimeetr_list)

knitr::kable(scilist(scimeetr_list), format = "markdown")

With the parameter k, we can control the length of the reading list.

scilist(scimeetr_list, k = 3)

knitr::kable(scilist(scimeetr_list, k = 3), format = "markdown")

With the parameter reading_list, we can get any of the following 12 reading lists that fits into three categories:

• Core
  • core_papers
  • core_yr
  • core_residual
• Experts
  • by_expert_LC
  • by_expert_TC
  • group_of_experts_TC
  • group_of_experts_LC
• Centrality
  • cite_most_others
  • betweeness
  • closeness
  • connectness
  • page_rank

The default reading list is core_papers.

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Core

I categorise the reading lists as core because they are reading lists of core papers as they are all a variation of the number of times papers within our community of interest refers to the paper listed. Although the number of citation is not a perfect measure of a papers importance for a community it should be a good proxy. A weekness of the number of citation as a measure of papers importance is that not all citations are equal. For example, sometimes a paper is cited because it is criticized or because it contrasts with other findings. This as been realised by others before and some have attempted to fix it by creating the concept of influential citation. Influential citation is a great concept by to be calculated it requires advance text processing and access to the full text of each papers. As it is notoriosly time consuming to get full text and even harder to get it in the right format, we are left with citation count.

Most cited per year

Using scilist with reading_list = "core_yr" will list the most cited paper for each year from three years before present to ten years before present. The parameter k controls the number of paper per year to list.

scilist(scimeetr_list, reading_list = "core_yr", k = 2)

knitr::kable(scilist(scimeetr_list, reading_list = "core_yr", k = 2), format = "markdown")

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More cited than expected

Using scilist with reading_list = "core_residual" will list the papers that diverge most from the expected number of citation for this particular paper. This can be visualised in the figure below. The point that have the biggest difference between their frequency value and the fitted blue lines are listed in the core_residual reading list.

splt_cr <- split_cr(scimeetr_list) 
cr_df <- dplyr::inner_join(splt_cr, scimeetr_list$com1$cr, by = 'ID')
library(dplyr, quietly = T)
x <- cr_df %>%
      mutate(age=as.integer(stringr::str_extract(Sys.Date(), '^[0-9]{4}')) - as.integer(as.character(cr_df$year))) %>%
      filter(age <= 40 & age > 2) %>% 
      group_by(age) %>%
      top_n(n = 10, wt = Frequency.x) %>%
      select(record, Frequency.x, age) %>%
      arrange(age, desc(Frequency.x)) %>%
      ungroup()
library(ggplot2)
ggplot(x, aes(x = age, y = Frequency.x)) +
  geom_point()+
  geom_smooth(method = "gam", formula = y ~ s(x, k=10), se = FALSE)

Here is an example of the code and its result.

scilist(scimeetr_list, reading_list = "core_residual", k = 3)

knitr::kable(scilist(scimeetr_list, reading_list = "core_residual", k = 3), format = "markdown")

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Experts

The reading lists that I categorise as expert are built from authors information. Experts within a community are identified based on the number of papers they published and the number of times each of their papers are cited.

Recent paper of a few experts

Using scilist with reading_list = "by_expert_LC" we will get a list of recent papers by one or a few experts in the community. For the option by_expert_LC, authors are ranked based on their harmonic local H-index. The H-index is a measure of an other productivity and impact. An author with an H-index of 10 means that he has published at least 10 papers with 10 or more citation each. A local H-index means that only citations from other papers in the community are counted. A harmonic local H-index means that authors do not get the full credit for each citation their paper received. It is corrected depending on the authos position in the authors list. First authors gets most of the credit, then the last author gets the second most, and the authors gets credit as a proportion of their position. Once the authors harmonic-local-H-index is found they are ranked and the m most recent publication of the k most 'expert' authors are listed as a reading list.

scilist(scimeetr_list, reading_list = "by_expert_LC", k = 2, m = 2)

knitr::kable(scilist(scimeetr_list, reading_list = "by_expert_LC", k = 2, m = 2), format = "markdown")

Using scilist with reading_list = "by_expert_TC" instead of reading_list = "by_expert_LC", notice the _TC instead of the _LC will based the ranking calculation on total citation of it's publications instead of only the local citations.

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Paper of experts group

Using scilist with reading_list = "group_of_experts_LC" we will get a list of papers for which many authors are experts in the community. For this option, authors are assigned a harmonic local H-index like described in the previous section. But this time, a weighted sum of the harmonic-local-H-index of each authors of a paper is calculated.

scilist(scimeetr_list, reading_list = "group_of_experts_LC", k = 5)

knitr::kable(scilist(scimeetr_list, reading_list = "group_of_experts_LC", k = 5), format = "markdown")

Using scilist with reading_list = "group_of_experts_TC" instead of reading_list = "group_of_experts_LC", notice the _TC instead of the _LC will based the ranking calculation on total citation of it's publications instead of only the local citations.

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Centrality

Their are several measures of nodes centrality in graph theory. The most central papers of a community of papers can be found with scilist.

Betweeness

Betweeness measures the importance of a paper in connecting two clusters of papers. Papers with a high betweeness would therefore be a paper that tend to be more interdisciplinary.

scilist(scimeetr_list, reading_list = "betweeness", k = 5)

knitr::kable(scilist(scimeetr_list, reading_list = "betweeness", k = 5), format = "markdown")

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Closeness

Closeness measures the average number of link between a paper and all other papers. Papers with a high closeness would therefore be a paper that tend to have a large and wide list of citations.

scilist(scimeetr_list, reading_list = "closeness", k = 5)

knitr::kable(scilist(scimeetr_list, reading_list = "closeness", k = 5), format = "markdown")

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Connectness

Connectness measures the number of links a paper has. Papers with a high connectness would therefore be a paper that tend to have cited what most other studies cited.

scilist(scimeetr_list, reading_list = "connectness", k = 5)

knitr::kable(scilist(scimeetr_list, reading_list = "connectness", k = 5), format = "markdown")

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Page rank

Page rank was developped by Larry Page at google and it's a way to measure web page importance. The algorithm was applied to directed graph, so I am not sure of the consequence of applying it on the undirected graph that we have here.

scilist(scimeetr_list, reading_list = "page_rank", k = 5)

knitr::kable(scilist(scimeetr_list, reading_list = "page_rank", k = 5), format = "markdown")

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Cite most others

With the option cite_most_others, the papers that cite most other papers of the community can be found. This is not a centrality measure but it is also based on papers connection to each other. It should tend to find litterature review and recent papers that have an especially good grasp on the community.

scilist(scimeetr_list, reading_list = "cite_most_others", k = 5)

knitr::kable(scilist(scimeetr_list, reading_list = "cite_most_others", k = 5), format = "markdown")

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Finding the main communities of research

In the previous sections we have looked at only the main research community. But, splitting the main community in sub-communities can provide a more detail picture of the litterature. It can also help identify and then remove irrelevant sub-communities. To achieve any of this, the sub-communities have to be identified and characterized. The function scimap, as in science map, was developped for this task. By default, the graph use bibliographic coupling to calculate connections between papers, but coupling can also be done based on abstract words (abc), title words (tic) or keywords (kec).

summary(scimap(scimeetr_list, coupling_by = 'bic', community_algorithm = 'louvain', min_com_size = 100))
summary(scimap(scimeetr_list, coupling_by = 'abc', community_algorithm = 'louvain', min_com_size = 100))
summary(scimap(scimeetr_list, coupling_by = 'tic', community_algorithm = 'louvain', min_com_size = 100))
summary(scimap(scimeetr_list, coupling_by = 'kec', community_algorithm = 'louvain', min_com_size = 100))

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Focusing on a sub-community

With the function focus_on, it is possible to change focus on a sub-community.

scil <- scimap(scimeetr_list)
scil
subscil <- focus_on(scil, grab = 'com1_1')
subscil

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Dive to a sub-community

With the function dive_to, it is possible to move down to a sub-community and keep it's sub-communities.

scil <- scimap(scimap(scimeetr_list))
scil
subscil <- dive_to(scil, aim_at = 'com1_1')
subscil

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MaximeRivest/scimeetr documentation built on May 8, 2019, 9:51 a.m.