list.search | R Documentation |
Search a list recusively by an expression
list.search(.data, expr, classes = "ANY", n, unlist = FALSE)
.data |
A |
expr |
a lambda expression |
classes |
a character vector of class names that restrict the search.
By default, the range is unrestricted ( |
n |
the maximal number of vectors to return |
unlist |
|
list.search
evaluates an expression (expr
) recursively
along a list (.data
).
If the expression results in a single-valued logical vector and its
value is TRUE
, the whole vector will be collected If it results
in multi-valued or non-logical vector, the non-NA
values
resulted from the expression will be collected.
To search whole vectors that meet certain condition, specify the expression that returns a single logical value.
To search the specific values within the vectors, use subsetting in the
expression, that is, .[cond]
or lambda expression like
x -> x[cond]
where cond
is a logical vector used to
select the elements in the vector.
# Exact search x <- list(p1 = list(type='A',score=c(c1=9)), p2 = list(type=c('A','B'),score=c(c1=8,c2=9)), p3 = list(type=c('B','C'),score=c(c1=9,c2=7)), p4 = list(type=c('B','C'),score=c(c1=8,c2=NA))) ## Search exact values list.search(x, identical(., 'A')) list.search(x, identical(., c('A','B'))) list.search(x, identical(., c(9,7))) list.search(x, identical(., c(c1=9,c2=7))) ## Search all equal values list.search(x, all(. == 9)) list.search(x, all(. == c(8,9))) list.search(x, all(. == c(8,9), na.rm = TRUE)) ## Search any equal values list.search(x, any(. == 9)) list.search(x, any(. == c(8,9))) # Fuzzy search data <- list( p1 = list(name='Ken',age=24), p2 = list(name='Kent',age=26), p3 = list(name='Sam',age=24), p4 = list(name='Keynes',age=30), p5 = list(name='Kwen',age=31) ) list.search(data, grepl('^K\\w+n$', .), 'character') ## Not run: library(stringdist) list.search(data, stringdist(., 'Ken') <= 1, 'character') list.search(data, stringdist(., 'Man') <= 2, 'character') list.search(data, stringdist(., 'Man') > 2, 'character') ## End(Not run) data <- list( p1 = list(name=c('Ken', 'Ren'),age=24), p2 = list(name=c('Kent', 'Potter'),age=26), p3 = list(name=c('Sam', 'Lee'),age=24), p4 = list(name=c('Keynes', 'Bond'),age=30), p5 = list(name=c('Kwen', 'Hu'),age=31)) list.search(data, .[grepl('e', .)], 'character') ## Not run: list.search(data, all(stringdist(., 'Ken') <= 1), 'character') list.search(data, any(stringdist(., 'Ken') > 1), 'character') ## End(Not run)
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