Deleting rows in a numpy array iteratively

Question

My program needs to find the product of all the terms in a vector save for one row i, which is determined by a for loop. The numpy.delete function will not accept i as an input, only a number. Is there a workaround for this?

Example:

for i in range(some_range):
    arr=[some vector]
    section=np.delete(arr,i,axis=0)
    return prod(section)

This returns a ValueError: invalid entry message. The code works fine when I replace the i with 1. Is there any way to perform this operation while retaining the for loop?

Is your indentation correct? The way you have it here with the return inside the loop, it will only run once (making the loop pointless). — Blckknght
– Blckknght, Commented Oct 23, 2013 at 7:56

NPE · Accepted Answer · 2013-10-23 06:27:37Z

1

No need to delete anything. Just multiply the two subproducts (the elements before i and the elements after i):

In [10]: import numpy as np

In [11]: arr = np.arange(1, 10)

In [12]: i = 3

In [13]: np.prod(arr[:i]) * np.prod(arr[i+1:])
Out[13]: 90720

Like with your original code, you need to make sure that i is a valid index (if you don't, you'd get the product of the entire array).

edited Oct 23, 2013 at 6:27

answered Oct 23, 2013 at 6:22

NPE

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