On Fri, Jan 29, 2010 at 12:10 PM, <josef.p...@gmail.com> wrote: > On Fri, Jan 29, 2010 at 11:49 AM, David Huard <david.hu...@gmail.com> wrote: >> Hi, >> >> I have a 4D "array" with a given shape, but the array is never >> actually created since it is large and distributed over multiple >> binary files. Typical usage would be to take slices across the 4D >> array. >> >> I'd like to know what the shape of the resulting array would be if I >> took a slice out of it. >> That is, let's say my 4D array is A, I'd like to know >> >> A[ndindex].shape >> >> without actually creating A. >> >> ndindex should support all numpy constructions (integer, boolean, >> array, slice, ...). I am guessing something already exists to do this, >> but I just can't put my finger on it. > > trying out some things, just because it's a puzzling question > >>>> indi= (slice(2,5), np.arange(2), np.arange(3)[:,None]) >>>> np.broadcast(*indi).shape > (3, 2) > > I don't know if this is ok for all possible cases, (and there are some > confusing things with reordering axis, when slices and fancy indexing > is mixed) >
Hi josef, Where then do you specify the shape of the A array ? Maybe an example would be clearer: Let's say A's shape is (10, 1, 5, 20) and the index is [::2, ..., 0] A[::2, ..., 0] shape would be (5, 1, 5) The broadcast idea has potential, I'll toy with it. David > Josef > > > >> Thanks. >> >> David >> _______________________________________________ >> NumPy-Discussion mailing list >> NumPy-Discussion@scipy.org >> http://mail.scipy.org/mailman/listinfo/numpy-discussion >> > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > http://mail.scipy.org/mailman/listinfo/numpy-discussion > _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
