Dear R-users,
likely there is a simple solution for this problem, but I currently
cannot see it.
I basically would like to get from a matrix values in particular
positions which are the rows of another matrix, without using a
for-loop.
In other words: is there any way to avoid the for-loop in the following
simple example:
M1 <- matrix(1:20, ncol=2)
M2 <- rbind(c(1,1), c(2,1), c(3,2), c(5,2), c(8,1))
v <- numeric(nrow(M2))
for(i in 1:length(v)){
v[i] <- M1[M2[i,1], M2[i,2]]
}
Any suggestion would be welcome,
Ciao,
Carlo Giovanni Camarda
===========================================
Camarda Carlo Giovanni
PhD-Student
Max Planck Institute for Demographic Research
Konrad-Zuse-Strasse 1
18057 Rostock, Germany
Tel: +49 (0)381 2081 172
Fax: +49 (0)381 2081 472
[EMAIL PROTECTED]
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