Slice Numpy character array using a view

Question

Hi I would like to slice a Numpy character array to have the following effect:

a = np.array(['2014-04-02', '2015-06-01', '1990-03-31'], dtype='|S11')
a[:, (0, 1, 2, 3, 5, 6, 8, 9)]
['20140402', '20150601', '19900331']

Iv seen that you can convert the char array into a matrix which you can then slice, like so:

view = a.view(np.uint8).reshape(a.shape + (a.dtype.itemsize,))
view_slice = view[:, (0, 1, 2, 3, 5, 6, 8, 9)]
view_slice ([[50, 48, 52, 45, 52, 45, 50,  0],
             [50, 48, 53, 45, 54, 45, 49,  0],
             [49, 57, 48, 45, 51, 45, 49,  0]], dtype=uint8)

But then how do I convert the view matrix back into a character array?

You could np.char.replace(a,"-","")

Padraic Cunningham
– Padraic Cunningham

2015-06-24 16:56:23 +00:00
Commented Jun 24, 2015 at 16:56 — Padraic Cunningham
– Padraic Cunningham, Commented Jun 24, 2015 at 16:56

Thomas Leonard · Accepted Answer · 2015-06-24 16:42:25Z

1

here you go :

view_slice = view[:, (0, 1, 2, 3, 5, 6, 8, 9)] # your slicing was not correct
view_slice.ravel().view(np.dtype('|S8'))
# array(['20140402', '20150601', '19900331'], dtype='|S8')

answered Jun 24, 2015 at 16:42

Thomas Leonard

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