Why is it that this line take ~30 sec to execute on a 500 MHz pentium III 128Meg RAM ? data1 = choose(greater(data,z2),(data,z2)) where data is a 2048x2080 array of float and z2 is a float. I thought that NumPy functions where written in C for faster execution. Or maybe that I'm wrong and this is fast execution? Thanks, Hugues Demers