Deleting certain elements from numpy array using conditional checks

Question

I want to remove some entries from a numpy array that is about a million entries long.

This code would do it but take a long time:

a = np.array([1,45         


        

Answer 1

You can use masked index with inversed condition.

>>> a = np.array([1,45,23,23,1234,3432,-1232,-34,233])

>>> a[~((a < -100) | (a > 100))]
array([  1,  45,  23,  23, -34])

>>> a[(a >= -100) & (a <= 100)]
array([  1,  45,  23,  23, -34])

>>> a[abs(a) <= 100]
array([  1,  45,  23,  23, -34])