proc iml;
a={1 2 3 ,1 2 3 , 1 2 3 };
temp1=1:ncol(a);
temp2=(1:nrow(a))`;
col=repeat(temp1,ncol(a),1);
row=repeat(temp2,1,nrow(a));
a[loc(row<col)]=j(1,ncol(loc(row<col)),0);
b=a[loc(row>=col)];
print a b;
quit;