Wolfram Fischer wrote:

I have e.g.
    t <- matrix( nrow=2, ncol=3, byrow=TRUE, c('a1','a2','a3','b1','b2','b3') )
and
    i <- c( 3, 2)

Is it possible to formulate a simple expression that gets
    c( t[ 1, i[1] ], t[ 2, i[2] ] )
(and so on for longer matrices)?

The result would be:
    [1] "a3" "b2"


Two solutions are (there might be better ones):

a)
  mapply(function(x,y) t[x,y], 1:nrow(t), i)
b)
  t(t)[i + (1:nrow(t) - 1) * (ncol(t))]

Note that calling the matrix "t" is not the best idea.

Uwe Ligges


Thanks - Wolfram

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