Modifying arrays with Operators and Iteration Numpy Python

Question

The function a[a.size - (a >= 0)[::-1].argmax():] = 0 assigns 0 to the arrays if the array is equal to or less than 0, it also assigns 0 to the arrays that are behind it. In example a the function works fine it assigns 0 to third element till the last element. However in example b it does not do that even though the initial value is negative. How could i modify the function so that it gives me the desired result.

Example A

a = np.array([[  123.7   131.1 -4578.2 -4579.1 -4520.1 -4561.3 -4490.9 -4498.5 -4513.8
 -4550.9]])
a[a.size - (a >= 0)[::-1].argmax():] = 0
Output = [123.7 131.1   0.    0.    0.    0.    0.    0.    0.    0. ]

Example B

b = np.array([-570.,  -593.37,   -286.59771,  -264.24308862])
b[b.size - (b >= 0)[::-1].argmax():] = 0
Output = [-570.,  -593.37,   -286.59771,  -264.24308862]
Desired Output = [0, 0, 0, 0]

I think the array a has one extra dimension since I copied your code and it didn't give me the output. You might edit that. — Nima S
– Nima S, Commented Feb 8, 2021 at 6:36

Pablo C · Accepted Answer · 2021-02-08 06:38:51Z

1

You can do it with a similar approach:

b[(b>=0).argmin():] = 0

(It also works for a)

answered Feb 8, 2021 at 6:38

Pablo C

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