Hi there, I need to find out within a loop whether a matrix is empty or not, e.g.: <hansl> nulldata 100 matrix test={} loop i=1..20 -q catch inv(test) if $error print "WRONG" endif endloop <hansl> Which is not working. Without the loop "WRONG" is printed as in <hansl> nulldata 100 matrix test={} catch inv(test) if $error print "WRONG" endif <hansl> Please help me with this problem. Cheers Leon