Interspersed below.
--------------------------------------------
Subject: Re: ifelse() woes ... can we agree on a ifelse2() ?
To: r-de...@lists.r-project.org
Date: Sunday, 27 November, 2016, 12:14 AM
On current 'ifelse' code in R:
...
* If 'test' is a factor, doing
storage.mode(test) <- "logical"
is not appropriate, but is.atomic(test) returns TRUE. Maybe use
if(!is.object(test))
instead of
if(is.atomic(test)) .
===================================
I now see that, for 'test' that is atomic and has "class" attribute, with
current 'ifelse' code, changing
if(is.atomic(test))
to
if(!is.object(test))
removes class of 'test' and makes the result doesn't have class of 'test',
which is not according to the documentation. The documentation of 'ifelse' says
that the value is "A vector of the same length and attributes (including
dimensions and "class") as 'test' ...".
===================================
function(test, yes, no, NA. = NA) {
if(!is.logical(test))
test <- if(isS4(test)) methods::as(test, "logical") else
as.logical(test)
n <- length(test)
n.yes <- length(yes); n.no <- length(no)
if (n.yes != n) {
if (n.no == n) { # swap yes <-> no
test <- !test
ans <- yes; yes <- no; no <- ans
n.no <- n.yes
} else yes <- yes[rep_len(seq_len(n.yes), n)]
}
ans <- yes
if (n.no == 1L)
ans[!test] <- no
else
ans[!test & !is.na(test)] <- no[
if (n.no == n) !test & !is.na(test)
else rep_len(seq_len(n.no), n)[!test & !is.na(test)]]
stopifnot(length(NA.) == 1L)
ans[is.na(test)] <- NA.
ans
}
===================================
For data frame, indexing by logical matrix is different from indexing by
logical vector.
Because there is an example like that, I think that it is better to remove
if(!is.logical(test))
in the function definition above, making 'as.logical' also applied to 'test' of
mode "logical", stripping attributes. Doing so makes sure that 'test' is a
plain logical vector, so that indexing is compatible with 'length'.
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