Extract the same element from the sublists of a list
Given a list of lists, this function can be used to extract a named element from each sublist.
subListExtract(L, name, simplify = FALSE, keep.names = TRUE)
L |
A list of named lists |
name |
The name of the element in the sublists that should be extracted. This should be a length one character vector. |
simplify |
When |
keep.names |
If |
This function is implemented in C and is intended to be faster than
calling lapply or sapply.
If simplify=FALSE, a list will be returned having the same
length as L, but with each element containing the
element named name from the corresponding inner list of
L.
When simplify=TRUE, an atomic vector will be returned
containing the extracted elements. If any of the inner list elements
do not have length one or cannot be put inside an atomic vector, an
error will be raised.
Seth Falcon
list_size = 500000
innerL = list(foo="foo", bar="bar")
L = rep(list(innerL), list_size)
system.time({j0 = sapply(L, function(x) x$foo)})
system.time({j1 = subListExtract(L, "foo", simplify=TRUE)})
stopifnot(all.equal(j0, j1))
LS = L[1:3]
names(LS) = LETTERS[1:3]
subListExtract(LS, "bar", simplify=TRUE)
subListExtract(LS, "bar", simplify=FALSE)
subListExtract(LS, "bar", simplify=TRUE, keep.names=FALSE)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.