Question

I have 2 arrays:

mask: with value 0 and 1, dtype=uint8

>>> mask
array([[0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       [1, 1, 1, ..., 0, 0, 0],
       ..., 
       [1, 1, 1, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0]], dtype=uint8)

and prova_clip

>>> prova_clip
array([[289, 281, 271, ..., 257, 255, 255],
       [290, 284, 268, ..., 260, 260, 259],
       [294, 283, 264, ..., 265, 263, 257],
       ..., 
       [360, 359, 360, ..., 335, 338, 331],
       [359, 364, 369, ..., 337, 342, 339],
       [358, 363, 368, ..., 332, 331, 332]], dtype=uint16)

I wish to use a code saving method to mask prova_clip with mask in order to have

array([[0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       [294, 283, 264, ..., 0, 0, 0],
       ..., 
       [360, 359, 360, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0],
       [0, 0, 0, ..., 0, 0, 0]], dtype=uint16)

Answer 1

Am I missing something? This seems as simple as:

prova_clip*mask

Here’s an example:

>>> a = np.arange(10,dtype=np.uint16)
>>> mask = np.ones(10,dtype=np.uint8)
>>> mask[1:3] = 0
>>> a*mask
array([0, 0, 0, 3, 4, 5, 6, 7, 8, 9], dtype=uint16)

---

You could also do it the complicated way which will modify an array in place.

>>> b = np.arange(10,dypte=np.uint16)
>>> b[~mask.astype(bool)] = 0
>>> b
array([0, 0, 0, 3, 4, 5, 6, 7, 8, 9], dtype=uint16)

---

Finally, there’s numpy.where:

>>> c = np.arange(10,dtype=np.uint8)
>>> np.where(mask==0,0,c)
array([0, 0, 0, 3, 4, 5, 6, 7, 8, 9], dtype=uint16)