peter leonard wrote: > I have a 4x4 matrix named 'lookup' with the following values: [...] > I then create a new empty matrix named 'dd' with specfic row and col > names : > > 1 3 4 3 3 1 > 1 NA NA NA NA NA NA > 2 NA NA NA NA NA NA > 3 NA NA NA NA NA NA > 4 NA NA NA NA NA NA > 3 NA NA NA NA NA NA > 2 NA NA NA NA NA NA > 1 NA NA NA NA NA NA > > I want to be able populate the cells in 'dd' using 'lookup' based on the > specified rownames and colnames of 'dd'. For example, the cell in 'dd'
If an R matrix is subscripted by an n by 2 matrix of row,column index pairs then the result is a vector of length n with the corresponding values taken from that matrix. Thus, suppose: rn <- c(1:4,3:1) cn <- c(1,3,4,3,3,1) Then dd strung out into a vector is: dd.vec <- lookup[as.matrix(expand.grid(rn,cn))] and reshaping this vector into a matrix gives: dd <- matrix(result.vec,nr=length(rn)) ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
