Would it be preferable to have to_begin='first' as an option under the existing kwarg to avoid overlapping?

On Wed, Oct 26, 2016 at 3:35 PM, Peter Creasey < p.e.creasey...@googlemail.com> wrote: > > Date: Wed, 26 Oct 2016 09:05:41 -0400 > > From: Matthew Harrigan <harrigan.matt...@gmail.com> > > > > np.cumsum(np.diff(x, to_begin=x.take([0], axis=axis), axis=axis), > axis=axis) > > > > That's certainly not going to win any beauty contests. The 1d case is > > clean though: > > > > np.cumsum(np.diff(x, to_begin=x[0])) > > > > I'm not sure if this means the API should change, and if so how. Higher > > dimensional arrays seem to just have extra complexity. > > > >> > >> I like the proposal, though I suspect that making it general has > >> obscured that the most common use-case for padding is to make the > >> inverse of np.cumsum (at least that?s what I frequently need), and now > >> in the multidimensional case you have the somewhat unwieldy: > >> > >> >>> np.diff(a, axis=axis, to_begin=np.take(a, 0, axis=axis)) > >> > >> rather than > >> > >> >>> np.diff(a, axis=axis, keep_left=True) > >> > >> which of course could just be an option upon what you already have. > >> > > So my suggestion was intended that you might want an additional > keyword argument (keep_left=False) to make the inverse np.cumsum > use-case easier, i.e. you would have something in your np.diff like: > > if keep_left: > if to_begin is None: > to_begin = np.take(a, [0], axis=axis) > else: > raise ValueError(‘np.diff(a, keep_left=False, to_begin=None) > can be used with either keep_left or to_begin, but not both.’) > > Generally I try to avoid optional keyword argument overlap, but in > this case it is probably justified. > > Peter > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > https://mail.scipy.org/mailman/listinfo/numpy-discussion >

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