I have a row vector R and a column vector C. I want to add them to create an array A with height equal to size of R and width equal to size of C as follows: A[i,j] = R[i] + C[j]
What's the most efficient way of doing this?
Asked
Active
Viewed 1,171 times
1 Answers
2
R + C[:, numpy.newaxis]
Does the trick for me.
For example
import numpy as np
r = np.ones(5)
c = np.ones(4) * 2
r + c[:, np.newaxis]
gives
array([[ 3., 3., 3., 3., 3.],
[ 3., 3., 3., 3., 3.],
[ 3., 3., 3., 3., 3.],
[ 3., 3., 3., 3., 3.]])
Jakub Bartczuk
- 2,317
- 1
- 20
- 27
-
1Maybe in your example values `r = np.arange(5)` and `c = np.arange(4) * 10` would better illustrate that we get the desired output. :) – Radek Dec 20 '17 at 22:39
-
this is interesting. – Aksakal almost surely binary Dec 21 '17 at 01:53
-
thanks, this worked. do you have a solution for a related question I posted? https://stackoverflow.com/questions/47916950/whats-the-most-efficient-way-to-increment-an-array-by-a-reference-while-broadca?noredirect=1&lq=1 – Aksakal almost surely binary Dec 21 '17 at 14:10