Python: sorting an array with another array's elements as keys?

Question

import numpy as np
x = np.array(range(10 * 30)).reshape(100, 3)
y = np.array(range(1010, 10, -10))
res = sorted(x, key = lambda y:y) #ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()
res = sorted(x, key=y) #TypeError: 'tuple' object is not callable

What is your question/problem, and what are you trying to do? It would be nice to have some more description instead of just posting code. — Karmastan
– Karmastan, Commented Feb 26, 2011 at 18:22

wisty · Accepted Answer · 2011-02-27 07:58:48Z

2

Try argsort:

import numpy as np
x = np.array(range(10 * 30)).reshape(100, 3)
y = np.array(range(1010, 10, -10))
args = y.argsort(axis = 0)
print x[args]

edited Feb 27, 2011 at 7:58

answered Feb 26, 2011 at 18:20

wisty

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2 Comments

senderle Over a year ago

This is cool -- but perhaps this should be args = y.argsort() and print x[args]? At least that seems to be what the OP is asking for...

chimichanga Over a year ago

Yeah you have to change the two last lines like senderle said but that's what I wanted thanks.

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