epmc_hits_trend function

Get the yearly number of hits for a query and the total yearly number of hits for a given period

epmc_hits_trend(query, synonym = TRUE, data_src = "med", period = 1975:2016)

Arguments

• query: query in the Europe PMC syntax

• synonym: logical, synonym search. If TRUE, synonym terms from MeSH terminology and the UniProt synonym list are queried, too. Disabled by default.

• data_src: character, data source, by default Pubmed/MedLine index (med) will be searched. The following three letter codes represent the sources, which are currently supported

  • agr: Agricola is a bibliographic database of citations to the agricultural literature created by the US National Agricultural Library and its co-operators.
  • cba: Chinese Biological Abstracts
  • ctx: CiteXplore
  • eth: EthOs Theses, i.e. PhD theses (British Library)
  • hir: NHS Evidence
  • med: PubMed/Medline NLM
  • nbk: Europe PMC Book metadata
  • pat: Biological Patents
  • pmc: PubMed Central
  • ppr: Preprint records

• period: a vector of years (numeric) over which to perform the search

Returns

a data.frame (dplyr tbl_df) with year, total number of hits (all_hits) and number of hits for the query (query_hits)

Details

A similar function was used in https://masalmon.eu/2017/05/14/evergreenreviewgraph/ where it was advised to not plot no. of hits over time for a query, but to normalize it by the total no. of hits.

Examples

## Not run:

# aspirin as query
epmc_hits_trend('aspirin', period = 2006:2016, synonym = FALSE)
# link to cran packages in reference lists
epmc_hits_trend('REF:"cran.r-project.org*"', period = 2006:2016, synonym = FALSE)
# more complex with publication type review
epmc_hits_trend('(REF:"cran.r-project.org*") AND (PUB_TYPE:"Review" OR PUB_TYPE:"review-article")',
period = 2006:2016, synonym = FALSE)
## End(Not run)