numpy.nanvar () in Python

numpy.nanvar (arr, axis = None) : compute the variance of data (array elements) along the specified axis (if any), ignoring NaN values.

Example :

x = 1 1 1 1 1
Standard Deviation = 0. Variance = 0

y = 9, 2, 5, 4, 12, 7, 8, 11, 9, 3, 7, 4, 12, 5, 4, 10, 9, 6, 9, 4

Step 1: Mean of distribution 4 = 7
Step 2: Summation of (x – x.mean ()) * * 2 = 178
Step 3: Finding Mean = 178/20 = 8.9
This Result is Variance.

Parameters:
arr: [array_like] input array.
axis: [int or tuples of int] axis along which we want to calculate the variance. Otherwise, it will consider arr to be flattened (works on all the axis). axis = 0 means variance along the column and axis = 1 means variance along the row.
out: [ndarray, optional] Different array in which we want to place the result. The array must have the same dimensions as expected output.
dtype: [data-type, optional] Type we desire while computing variance.

Results: Variance of the array (a scalar value if axis is none) or array with variance values ​​along specified axis; while ignoring NaN values.

Code # 1:

# Python program illustrating
# numpy.nanvar () method

import numpy as np 

 
# 1D array

arr = [ 20 , 2 , np.nan, 1 , 34

 

print ( " arr: " , arr) 

print ( "nanvar of arr:" , np.nanvar (arr)) 

 

print ( "var of arr:" , np.var (arr)) 

  

print ( "nanvar of arr:" , np.nanvar (arr, dtype = np.float32)) 

print ( "var of arr:" , np.var (arr , dtype = np.float32)) 

 

Output:

 arr: [20, 2, nan, 1, 34] nanvar of arr: 187.1875 var of arr: nan nanvar of arr: 187.1875 var of arr: nan 

Code # 2:

# Python program illustrating
# numpy.nanvar () method

import numpy as np 

 

 
# 2D array

arr = [[ 2 , 2 , 2 , 2 , 2 ],  < / p>

[ 15 , 6 , np.nan, 8 , 2 ], 

[ 23 , 2 , 54 , 1 , 2 , ], 

[np.nan, 44 , 34 , 7 , 2 ]] 

  

 
# flattened array nanvar

print ( "nanvar of arr, axis = None : " , np.nanvar (arr)) 

  

print ( "var of arr, axis = None:" , np.var (arr)) 

 

 
# nanvar along axis = 0

print ( "nanvar of arr, axis = 0:" , np.nanvar (arr, axis = 0 )) 

  

print ( "var of arr, axis = 0 : " , np.var (arr, axis = 0 )) 

 
# nanwar along axis = 1

print ( " nanvar of arr, axis = 1: " , np.nanvar (arr, axis = 1 )) 

Output:

 nanvar of arr, axis = None: 249.88888888888889 var of arr, axis = None: nan nanvar of arr, axis = 0: [ 74.88888889 312.75 458.66666667 9.25 0.] var of arr, axis = 0: [nan 312.75 nan 9.25 0.] nanvar of arr, axis = 1: [0. 22.1875 421.84 313.1875]