On 23-Aug-03 Douglas G. Scofield wrote: > What's the best way in R to fill a matrix who's entries depend on some > function of the indices? I'm currently doing: > > Q <- matrix(0, k, k) > for (A in 1:k) { > for (B in 1:k) { > Q[A,B] <- my.function(A,B) > } > } > > but I wonder if there is a more terse way.
Something on the following lines? > xx<-matrix(rep(c(1,2,3),3),ncol=3) > xx [,1] [,2] [,3] [1,] 1 1 1 [2,] 2 2 2 [3,] 3 3 3 > yy<-t(xx) > yy [,1] [,2] [,3] [1,] 1 2 3 [2,] 1 2 3 [3,] 1 2 3 > myfun<-function(XX,YY){(XX-YY)^2} > myfun(xx,yy) [,1] [,2] [,3] [1,] 0 1 4 [2,] 1 0 1 [3,] 4 1 0 [The above is inspired by the matlab/octave function "meshdom"] Best wishes, Ted. -------------------------------------------------------------------- E-Mail: (Ted Harding) <[EMAIL PROTECTED]> Fax-to-email: +44 (0)870 167 1972 Date: 23-Aug-03 Time: 22:25:07 ------------------------------ XFMail ------------------------------ ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help