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

period

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

Value

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 http://www.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)
# }