match()/%in% with language objects?
match(x,table) and x%in%table work when x and table are lists of language objects or expressions. E.g., expression(quote(1+2), quote(log2(16))) %in% expression(3, quote(1+2), c(4L,5L,6L,7L)) #[1] TRUE FALSE list(quote(1+2), quote(log2(16))) %in% list(3, quote(1+2), c(4L,5L,6L,7L)) #[1] TRUE FALSE match(list(quote(1+2), quote(log2(16))), list(3, quote(1+2), c(4L,5L,6L,7L))) #[1] 2 NA With your example data: spList[1] %in% spList #[1] TRUE list(quote(foo)) %in% spList #[1] TRUE list(quote(nosuchsymbol)) %in% spList #[1] FALSE Bill Dunlap TIBCO Software wdunlap tibco.com
On Tue, Aug 25, 2015 at 9:12 AM, Ben Bolker <bbolker at gmail.com> wrote:
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I haven't yet dug into the internals of match() yet to see what's
going on, but I'm wondering whether there's a design reason why I
can't use %in% (which is a wrapper for match()) on language objects.
I'd like to test whether a language object is in a list of language
objects, but I get the error "'match' requires vector arguments":
specials <- c("foo","bar")
spList <- lapply(specials,as.name) ## convert to language objects
"a" %in% spList ## works (FALSE)
spList[[1]] %in% spList ## 'match' requires vector arguments
quote(foo) %in% spList ## ditto
quote(foo) == spList[[1]] ## TRUE
obviously I can go the other way, converting my target into text:
deparse(spList[[1]]) %in% specials ## TRUE
I could also write my own function to loop through the list and stop
when I find it. But I'd prefer to use built-in functionality if possible.
Does anyone have any clues/see what I'm missing?
cheers
Ben Bolker
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