numpy.percentile () in python

Michael Zippo 18.07.2021

numpy.percentile() used to calculate the n-th precentile of data (array elements) along the specified axis.

Syntax: numpy.percentile (arr, n, axis = None, out = None)
Parameters:
arr: input array.
n: percentile value.
axis: axis along which we want to calculate the percentile value. Otherwise, it will consider arr to be flattened (works on all the axis). axis = 0 means along the column and axis = 1 means working along the row.
out: Different array in which we want to place the result. The array must have same dimensions as expected output.

Return: nth Percentile of the array (a scalar value if axis is none) or array with percentile values along specified axis.

Code # 1: Work

# Python program illustrating
# numpy.percentile () method

import numpy as np

# 1D array

arr = [ 20 , 2 , 7 , 1 , 34 ]

print ( "arr:" , arr)

print ( " 50th percentile of arr: " ,

np.percentile (arr, 50 ))

print ( "25th percentile of arr:" ,

np.percentile (arr, 25 ))

print ( "75th percentile of arr:" ,

np.percentile (arr, 75 ))

Output:

 arr: [20, 2, 7, 1, 34] 30th percentile of arr: 7.0 25th percentile of arr: 2.0 75th percentile of arr: 20.0

Code # 2:

# Python program illustrating
# numpy.percentile () method

import numpy as np

# 2D array

arr = [[ 14 , 17 , 12 , 33 , 44 ],

[ 15 , 6 , 27 , 8 , 19 ],

[ 23 , 2 , 54 , 1 , 4 ,]]

print ( "arr:" , arr)

# Flattened array percentile

print ( "50th Percentile of arr, axis = None:" ,

np.percentile (arr, 50 ))

print ( "0th Percentile of arr, axis = None:" ,

np.percentile (arr, 0 ))

# Axis percentile = 0

print ( "50th Percentile of arr, axis = 0:" ,

np.percentile (arr, 50 , axis = 0 ))

print ( "0th Percentile of arr, axis = 0: " ,

np.percentile (arr, 0 , axis = 0 ))

Output:

 arr: [[14, 17, 12, 33, 44], [15, 6, 27, 8 , 19], [23, 2, 54, 1, 4]] 50th Percentile of arr, axis = None: 15.0 0th Percentile of arr, axis = None: 1.0 50th Percentile of arr, axis = 0: [15. 6. 27. 8. 19.] 0th Percentile of arr, axis = 0: [14. 2. 12. 1. 4.] 50th Percentile of arr, axis = 1: [17. 15. 4.] 0th Percentile of arr, axis = 1: [12. 6. 1.]

Code # 3:

# Python program illustrating
# numpy.percentile () method

import numpy as np

# 2D array

arr = [[ 14 , 17 , 12 , 33 , 44 ],

[ 15 , 6 , 27 , 8 , 19 ],

[ 23 , 2 , 54 , 1 , 4 ,]]

print ( "arr:" , arr)

# Axis percentile = 1

print ( " 50th Percentile of arr, axis = 1: " ,

   np.percentile (arr,   50  , axis   =   1  )) 
   print   (  "0th Percentile of arr, axis = 1:"  , 
   np.percentile (arr,   0  , axis   =   1  ))  
   
   print   (  "0th Percentile of arr, axis = 1:"  , 
   np.percentile (arr,   50  , axis   =   1  , keepdims   =   True  ))  
   print   (  "0th Percentile of arr, axis = 1: " , 
     np. percentile (arr,   0  , axis   =   1  , keepdims   =   True  ))

Output:

 arr: [[14, 17, 12, 33, 44], [15, 6, 27, 8, 19], [23, 2, 54, 1 , 4]] 0th Percentile of arr, axis = 1: [[17.] [15.] [4.]] 0th Percentile of arr, axis = 1: [[12.] [6.] [1.]]