> > Hi, probably a basic question, but I'm looking for a neat way to sum > all the positive values in an array of floats. I'm currently doing it > the hard way, but am hoping there is some cunning and elegant syntax I > can use instead
Fancy indexing's my favorite cunning and elegant syntax: a = numpy.random.randn(100) a.sum() a > 0 # gives a boolean array that's True where the elements of a are > 0. a[a > 0] # retrieve from a only the elements with True in the boolean array. a[a > 0].sum() # your desired result. Note that you can also fancy-index with a list/array of indices, as well as a boolean "mask" array: a[[1, 40, 55]] # pulls just the values at index 1, 40, and 55 out of a into a shape (3,) array. Zach _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
