I have two arrays v and c (can read as value and cost).
I need to perform argsort() on v such that if 2 elements in v are the same, then they need to be sorted according to their corresponding elements in c.
Example
v = [4,1,4,4] # Here 0th, 2nd and 3rd elemnt are equal
c = [5,0,30,10]
numpy.argsort(v) = [1,0,2,3] # equal values sorted by index
Required output
[1,0,3,2] # c[0] < c[3] < c[2]
How to achieve this in Python?
The function argsort receives an order parameter, from the docs:
When a is an array with fields defined, this argument specifies which fields to compare first, second, etc.
So you could create a structured array from the two values, and the pass the fields in order:
import numpy as np
v = [4, 1, 4, 4]
c = [5, 0, 30, 10]
s = np.array(list(zip(v, c)), dtype=[('value', 'i4'), ('cost', 'i4')])
result = np.argsort(s, order=['value', 'cost'])
print(result)
Output
[1 0 3 2]