How to sort a 2D array by a column in numpy?

How to sort a 2D array by a column in numpy?

How to sort a 2D array by a column in numpy?

This recipe helps you sort a 2D array by a column in numpy


Recipe Objective

How to sort a 2D array by a column. yes we can do this and for that we have to use the "sort" function available in the numpy library. In this if we want to sort 2D numpy array by 2nd column then we have to change the positions of all the rows based on the sorted values of the column (2nd column) with an column index for e.g 1 we can say.

Step 1 - Import library

import numpy as np

Step 2 - Take a Sample array

Sample_array = np.array([[100, 101, 500, 104], [201, 202, 203, 204], [301, 300, 600, 307]]) print("This is Sample 2D array :","\n", Sample_array)
This is Sample 2D array : 
 [[100 101 500 104]
 [201 202 203 204]
 [301 300 600 307]]

Step 3 - Sort Sample array

Index = 2 Array_sort = Sample_array[Sample_array[:,Index].argsort()] print("The original array is:","\n","\n", Sample_array, "\n") print("The sorted array is:", "\n", "\n", Array_sort)
The original array is: 
 [[100 101 500 104]
 [201 202 203 204]
 [301 300 600 307]] 

The sorted array is: 
 [[201 202 203 204]
 [100 101 500 104]
 [301 300 600 307]]

Here we can see the array has been sorted according to the given Index number that we have passed in "Indexed" variable i.e 2. So we can see the 3rd column is been sorted now as before it was not.

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