Comparing Paul's solution to mine I found a typo in my previous post: > i = REBIN(REFORM(FINDGEN(n),n,1,1),n,n,n)^2 ; x^2 > > a = i + $ ; x^2 > > TRANSPOSE(i,[1,0,2]) + $ ; y^2 > > TRANSPOSE(i,[0,2,1]) ; z^2 > ^^^^^^ should read [2,1,0] -- Benno Puetz Kernspintomographie Max-Planck-Institut f. Psychiatrie Tel.: +49-89-30622-413 Kraepelinstr. 10 Fax : +49-89-30622-520 80804 Muenchen, Germany