Applying formula based on condition in numpy array

Question

I have numpy array:

wk = np.array([1, 0, 3, -4])

how to apply a formula based on certain condition, like how to sum all positive value in wk. I've tried

if wk.all > 0:
    np.sum(wk)

But it threw an error.

TypeError: '>' not supported between instances of 'builtin_function_or_method' and 'int' — dzdws
– dzdws, Commented Sep 16, 2021 at 15:42

Homan · Accepted Answer · 2021-09-16 15:43:40Z

3

np.sum(wk[wk > 0])

is what you are looking for. wk > 0 creates a boolean array of the same size as wk that is true everywhere where wk > 0. wk[wk > 0] then evaluates to an array that only contains those elements of wk where the former array is true and finally np.sum sums up those values.

answered Sep 16, 2021 at 15:43

Homan

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Comments

Tanish Surana · Accepted Answer · 2021-09-16 15:47:04Z

1

for the positive values you can use:

import numpy as np
wk = np.array([1, 0, 3, -4])
sum = wk[wk>0].sum() # returns array of elements which are positive and then adds them

similarly you can put conditions inside wk[condition_here]

answered Sep 16, 2021 at 15:47

Tanish Surana

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