On 08.02.2012 18:17, josef.p...@gmail.com wrote:
> I think I use it quite a bit, and I like that the broadcasting in
> indexing is as flexible as the broadcasting of numpy arrays
> themselves.
>
> x[np.arange(len(x)), np.arange(len(x))] gives the diagonal for example.
Personally I would prefer that a function like np.diag could return a
view. (The stride is regular, so why not?)
def diag(x):
return x.reshape(np.prod(x.shape))[::x.shape[0]+1]
>>> a = np.zeros((10,10))
>>> d = diag(a)
>>> d[:] = 2
>>> a
array([[ 2., 0., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 2., 0., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 2., 0., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 2., 0., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 2., 0., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 2., 0., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 2., 0., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 2., 0., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 2., 0.],
[ 0., 0., 0., 0., 0., 0., 0., 0., 0., 2.]])
Sturla
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