[R] matrix indexing

From: toka tokas <tokkass_at_yahoo.com>
Date: Thu 18 Aug 2005 - 19:02:13 EST


Dear R-users,

I was wondering for the following:

Let 'x' be a matrix and 'ind' and indicator matrix, i.e.,

x <- array(1:20, dim = c(4, 5))
ind <- array(c(1:3, 3:1), dim = c(3, 2))

I'd like to get (as a vector) the elements of 'x' which are not indexed by 'ind'. Since negative indices are not allowed in index matrices I thought of using something like:

x[ind] <- NA
x[!is.na(x)]

but are there any more elegant solutions.

Thanks in advance,
toka



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