numpy.argsort() function is used to perform an indirect sort along the given axis using the algorithm specified by the kind keyword. It returns an array of indices of the same shape as arr that would sort the array. It means indices of value arranged in ascending order
Syntax : numpy.argsort(arr, axis=-1, kind=’quicksort’, order=None)
Parameters:
- arr : [array_like] Input array.
- axis : [int or None] Axis along which to sort. If None, the array is flattened before sorting. The default is -1, which sorts along the last axis.
- kind : [‘quicksort’, ‘mergesort’, ‘heapsort’]Selection algorithm. Default is ‘quicksort’.
- order : [str or list of str] When arr is an array with fields defined, this argument specifies which fields to compare first, second, etc.
Return: [index_array, ndarray] Array of indices that sort arr along the specified axis.If arr is one-dimensional then arr[index_array] returns a sorted arr.
Code #1:
Python3
# Python program explaining# argpartition() functionimport numpy as geek# input arrayin_arr = geek.array([2, 0, 1, 5, 4, 1, 9])print("Input unsorted array : ", in_arr)out_arr = geek.argsort(in_arr)print("Output sorted array indices : ", out_arr)print("Output sorted array : ", in_arr[out_arr]) |
Output:
Input unsorted array : [2 0 1 5 4 1 9] Output sorted array indices : [1 2 5 0 4 3 6] Output sorted array : [0 1 1 2 4 5 9]
Code #2:
Python3
# Python program explaining# argpartition() functionimport numpy as geek# input 2d arrayin_arr = geek.array([[2, 0, 1], [5, 4, 3]])print("Input array : ", in_arr)# output sorted array indicesout_arr1 = geek.argsort(in_arr, kind='mergesort', axis=0)print("Output sorted array indices along axis 0: ", out_arr1)out_arr2 = geek.argsort(in_arr, kind='heapsort', axis=1)print("Output sorteded array indices along axis 1: ", out_arr2) |
Output:
Input array : [[2 0 1] [5 4 3]] Output sorted array indices along axis 0: [[0 0 0] [1 1 1]] Output sorted array indices along axis 1: [[1 2 0] [2 1 0]]
Code #3:
Python
# get two largest value from numpy arrayx=np.array([12,43,2,100,54,5,68])# using argsort get indices of value of arranged in ascending ordernp.argsort(x)#get two highest value index of arraynp.argsort(x)[-2:]# to arrange in ascending order of indexnp.argsort(x)[-2:][::-1]# to get highest 2 values from arrayx[np.argsort(x)[-2:][::-1]] |
Output:
array([2, 5, 0, 1, 4, 6, 3], dtype=int32) array([6, 3], dtype=int32) array([3, 6], dtype=int32) array([100, 68])
