CODEWITHSUNDEEP
python
3sm1r
3sm1r

Reputation: 530

Python's synthetic way to select negative components of a vector

if I have for example a vector like

import numpy as np
a=np.array([1,2,-3,4,-5])

if I want to create a vector b with the negative values of a I can of course do a for loop

list=[]
for i in a:
    if i<0:
        list.append(i)
b=np.array(list)

but I am sure that there is a better way. What is a more synthetic, python-ish way to do the same thing?

Upvotes: 0

Views: 71

Answers (2)

CJR
CJR

Reputation: 3985

Arrays are inherently able to be selected by a boolean array, so:

a=np.array([1,2,-3,4,-5])
b=a[a<0]

Gives

>>> b
array([-3, -5])

Upvotes: 2

wencakisa
wencakisa

Reputation: 5958

You can try with list comprehension:

b = np.array([i for i in a if i < 0])

Upvotes: 1

Related Questions