r - Inverse of which -
am missing obvious here? appears inverse function of which
missing base r (googling , search on "r inverse which" returns myriad of unrelated links)?
well, not can't write one, relieve frustration being missing , r-muscle flexing challenge: how go writing one?
what need function like:
invwhich<-function(indices, totlength)
that returns logical vector of length totlength
each element in indices
true
, rest false
.
there's bound lot of ways of accomplishing (some of low hanging fruit), argue why solution 'best'. oneliner anyone?
if takes account of other parameters of which
(arr.ind
??), that's better...
one-liner solution:
invwhich <- function(indices, totlength) is.element(seq_len(totlength), indices) invwhich(c(2,5), 10) [1] false true false false true false false false false false
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