Let’s see the program for how to get the n-largest values of an array using NumPy library. For getting n-largest values from a NumPy array we have to first sort the NumPy array using numpy.argsort() function of NumPy then applying slicing concept with negative indexing.
Syntax: numpy.argsort(arr, axis=-1, kind=’quicksort’, order=None)
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.
Let’s see an example:
Example 1: Getting the 1st largest value from a NumPy array.
# import library import numpy as np
# create numpy 1d-array arr = np.array([ 2 , 0 , 1 , 5 ,
4 , 1 , 9 ])
print ( "Given array:" , arr)
# sort an array in # ascending order # np.argsort() return # array of indices for # sorted array sorted_index_array = np.argsort(arr)
# sorted array sorted_array = arr[sorted_index_array]
print ( "Sorted array:" , sorted_array)
# we want 1 largest value n = 1
# we are using negative # indexing concept # take n largest value rslt = sorted_array[ - n : ]
# show the output print ( "{} largest value:" . format (n),
rslt[ 0 ])
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Output:
Given array: [2 0 1 5 4 1 9] Sorted array: [0 1 1 2 4 5 9] 1 largest value: 9
Example 2: Getting the 3-largest values from a NumPy array.
# import library import numpy as np
# create numpy 1d-array arr = np.array([ 2 , 0 , 1 , 5 ,
4 , 1 , 9 ])
print ( "Given array:" , arr)
# sort an array in # ascending order # np.argsort() return # array of indices for # sorted array sorted_index_array = np.argsort(arr)
# sorted array sorted_array = arr[sorted_index_array]
print ( "Sorted array:" , sorted_array)
# we want 3 largest value n = 3
# we are using negative # indexing concept # find n largest value rslt = sorted_array[ - n : ]
# show the output print ( "{} largest value:" . format (n),
rslt)
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Output:
Given array: [2 0 1 5 4 1 9] Sorted array: [0 1 1 2 4 5 9] 3 largest value: [4 5 9]