apply a function to each pair of rows of an array

Question

I have a numpy array of size 4x400. I want to apply a function to all pairs of rows of this numpy array. The function:

def func(vector1,vector2):
    ...
    ...
    return X

where X is a float value.

So in the end I will get a vector of length 10.

Is there any way to this efficiently (fast) without using loops?

I didnt downvote ... but you are likely going to give us a small self contained code example if you want an answer ... — Joran Beasley
– Joran Beasley, Commented Oct 28, 2014 at 16:18

Abhishek Thakur · Accepted Answer · 2014-10-28 16:39:26Z

4

import numpy
import itertools as it
arr=numpy.random.rand(4,400)
transposed=arr.T
values=[numpy.dot(i,j) for i, j in it.combinations(transposed, 2)]
print values

answered Oct 28, 2014 at 16:39

Abhishek Thakur

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Comments

Mujtaba Hasan · Accepted Answer · 2014-10-28 16:21:49Z

1

I think u will have to use loop. Use itertools in python to generate all combinations of rows This may help you https://docs.python.org/2/library/itertools.html.. Then apply your function on all generated pairs

answered Oct 28, 2014 at 16:21

Mujtaba Hasan

1126 bronze badges

2 Comments

Brandon Nadeau Over a year ago

Certainly need a loop or comprehension list. Loops are probably the most basic and needed programming skill. If your not efficient in loops I would seriously brush up on them, or else you will never be able to handle data.

Abhishek Thakur Over a year ago

did it. without loops. see my own answer.

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