Hi, I am also considering a switch from Matlab to NumPy/SciPy at some point. Note that in the last version of Matlab (7?) you don't have to use 'find', but you now can 'conditional arrays' as an index, so instead of idx=find(a>5); a(idx)=6; you can do: cond=a>5; a(cond) = 6; or even shorter a(a>5) = 6; Does someone know if the same trick is possible in NumPy? Cheers, Bas