2009/4/29 Dan Goodman <dg.gm...@thesamovar.net>: > Here's the problem I want to write vectorised code for. I start with an > array of indices, say I=array([0,1,0,2,0,1,4]), and I want to come up > with an array C that counts how many times each index has been seen so > far if you were counting through the array from the beginning to the > end, e.g. for that I, C=array([0,0,1,0,2,1,0]). This is easy enough to > do with a C loop, but trickier to do just with numpy. Any ideas?
This is not effective memory-wise, but it avoids the for-loop: np.diag(np.cumsum(x == x[:, None], axis=1)) - 1 Cheers Stéfan _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
