Python : find the indices of bins to which elements of an array belong

Question

I divided a list of numbers into k bins. Now I want to find the bin indices of each of the elements of the list. What Python function should I use for it?

Answer 1

The digitize() function of the Numpy module returns the indices of the bins to which each element of an input array belongs.

Here is an example to show how to use this function:

>>> import numpy as np
>>> bins = [0, 0.3, 0.6, 0.9, 1]
>>> a=[random.random() for _ in range(5)]
>>> a
[0.7241728528056117, 0.9554118020610317, 0.6996522756699897, 0.3270152713938511, 0.350725384946479]
>>> np.digitize(a,bins,right=False)
array([3, 4, 3, 2, 2])

In the above example, I have mentioned right=False, so the bin index will be assigned as follows:

0 <= x < 0.3 ---> 1st bin

0.3 <= x < 0.6 ---> 2nd bin

0.6 <= x < 0.9 ---> 3rd bin

0.9 <= x < 1 ---> 4th bin

The output shows that the first element, "0.7241728528056117," is in the 3rd bin, the second element is in the 4th bin, and so on.