The matrix r is (2*t-1)*(2*t-1) but is it empty..may you help me? Besides, I need to start the do from a negative number is this o.k.?? This is the program: proc iml; t=15; a=2*t; r=j(a-1,a-1,.);     do i= (1-t) to (t-1);         do j= (1-t) to (t-1);                 az1= -(j-i);         az2= -(j-i);         bz1= -(j-i);         bz2= (j-i);         cz1= (j-i);         cz2= (j-i);         if j<0 then z1=az1;         z2=az2;         if j=0 then z1=bz1;         z2=bz2;         if j>0 then z1=cz1;         z2=cz2;         r[i,j]=probnorm(z2)-probnorm(z1);         end;     end; print r; quit; Thanks in advance. Waiting for your reply. ... View more