Numpy arrays - Multidimensional logic comparison

Question

I am trying find the entries in a two-dimensional array that are above a certain threshold. The thresholds for the individual columns is given by a one-dimensional array. To exemplify,

[[1, 2, 3],
 [4, 5, 6],
 [2, 0, 4]]

is the two-dimensional array and I want to see if where in the columns values are bigger than

[2, 1, 3]

so the output of running the operation should be

[[False, True, False]
 [True, True, True],
 [False, False, True]]

Thanks!

Something is wrong in your example. For example, why a True value corresponds to 0? 0 is clearly smaller than all your thresholds. — ojy
– ojy, Commented Jul 29, 2014 at 0:12
Still does not compute :) 6 is greater than any element, but has a False value. — ojy
– ojy, Commented Jul 29, 2014 at 0:28

ojy · Accepted Answer · 2014-07-29 00:27:57Z

3

Well, assuming there's an error in the example, I would simply do:

import numpy as np

A = np.array([[1, 2, 3],[4, 5, 6],[2, 0, 4]])
T = np.array([2, 1, 3])

X = A > T

Which gives

array([[False,  True, False],
   [ True,  True,  True],
   [False, False,  True]], dtype=bool)

answered Jul 29, 2014 at 0:27

ojy

2,4922 gold badges20 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

heltonbiker Over a year ago

+1. This is why it happens: docs.scipy.org/doc/numpy/user/basics.broadcasting.html

p-robot · Accepted Answer · 2014-07-29 00:15:34Z

0

I think there may be inconsistencies in your example (e.g. 2 > 1 is True, yet 2 > 4 is True) - can you clarify this?

Assuming you you want to know, for each row, which columns of the values in the first list are greater than the [2,1,3] list you gave, I suggest the following:

import numpy as np

tmp = [[1, 2, 3],
      [4, 5, 6],
      [2, 0, 4]]

output = [ np.less([2, 1, 3], tmp[i]) for i in range(len(tmp))]

Similarly, try greater or greater_equal or less_equal for the result you're after: http://docs.scipy.org/doc/numpy/reference/routines.logic.html

answered Jul 29, 2014 at 0:15

p-robot

4,9353 gold badges33 silver badges44 bronze badges

Collectives™ on Stack Overflow

Numpy arrays - Multidimensional logic comparison

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related