Combines several terms into one 'Scopus' query string, optionally wrapping each in a field tag and joining them with a boolean operator. It is a tidier alternative to pasting query fragments together by hand, which is where field-tag and bracket mistakes tend to creep in.
Usage
scopus_query(..., .op = c("AND", "OR", "AND NOT"), .field = NULL)Arguments
- ...
Character terms to combine, for example
"language learning"and"effect size".- .op
The boolean operator joining the terms, one of
"AND","OR"or"AND NOT".- .field
Optional field tag applied to every term (see
scopus_field_tags()).
Value
A length-one character string suitable for scopus_count(),
scopus_fetch() or the query of scopus_plan().
Details
Each term is trimmed and, given .field, wrapped in that tag, whose
brackets hold the term together. Without a field tag, a term of several
words is put in brackets before two or more terms are joined, because
'Scopus' joins the words of an unquoted term with AND. Joined bare,
machine learning OR deep learning would read as
machine AND (learning OR deep) AND learning. A term that is already one
operand is left as written: a quoted "..." phrase, a braced {...}
phrase, a bracketed group or a single field-tagged group such as
TITLE(deep learning). Single words are never bracketed, so
scopus_query("CRISPR", "Cas9", .op = "OR") stays CRISPR OR Cas9, and a
query composed by an earlier call keeps its meaning when it is joined again.
A term that already opens with a field tag is refused when .field is
given, because the API rejects one tag nested inside another.
Examples
scopus_query("climate change", "adaptation", .field = "TITLE-ABS-KEY")
#> [1] "TITLE-ABS-KEY(climate change) AND TITLE-ABS-KEY(adaptation)"
scopus_query("graphene", "supercapacitor", .op = "AND")
#> [1] "graphene AND supercapacitor"
scopus_query("CRISPR", "Cas9", "Cas12", .op = "OR")
#> [1] "CRISPR OR Cas9 OR Cas12"
# Without a field tag, multi-word terms are bracketed and phrases kept as written.
scopus_query("machine learning", "deep learning", .op = "OR")
#> [1] "(machine learning) OR (deep learning)"
scopus_query('"heart attack"', '"myocardial infarction"', .op = "OR")
#> [1] "\"heart attack\" OR \"myocardial infarction\""