2008/5/19 Orest Kozyar <[EMAIL PROTECTED]>: > Given a slice, such as s_[..., :-2:], is it possible to take the > complement of this slice? Specifically, s_[..., ::-2]. I have a > series of 2D arrays that I need to split into two subarrays via > slicing where the members of the second array are all the members > leftover from the slice. The problem is that the slice itself will > vary, and could be anything such as s_[..., 1:4:] or s_[..., 1:-4:], > etc, so I'm wondering if there's a straightforward idiom or routine in > Numpy that would facilitate taking the complement of a slice? I've > looked around the docs, and have not had much luck.
If you are using boolean indexing, of course complements are easy (just use ~). But if you want slice indexing, so that you get views, sometimes the complement cannot be expressed as a slice: for example: A = np.arange(10) A[2:4] The complement of A[2:4] is np.concatenate((A[:2],A[4:])). Things become even more complicated if you start skipping elements. If you don't mind fancy indexing, you can convert your index arrays into boolean form: complement = A==A complement[idx] = False Anne _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
