Numpy MaskedArray.dot() function | Python

Last Updated : 18 Oct, 2019

numpy.MaskedArray.dot() function is used to calculate the dot product of two mask arrays.

Syntax : numpy.ma.dot(arr1, arr2, strict=False)

Parameters:
arr1, arr2:[ ndarray] Inputs arrays.
strict : [bool, optional] Whether masked data are propagated (True) or set to 0 (False) for the computation. Default is False.

Return : [ ndarray] The dot product of arr1 and arr2.

Code #1 :

# Python program explaining 
# numpy.MaskedArray.dot() method  
    
# importing numpy as geek   
# and numpy.ma module as ma  
import numpy as geek  
import numpy.ma as ma  
    
# creating input arrays    
in_arr1 = geek.array([[1, 2], [ 3, 4]]) 
print ("1st Input array : ", in_arr1)  
    
in_arr2 = geek.array([[-1, -2], [ -3, -4]])  
print ("2nd Input array : ", in_arr2)  
    
      
# Now we are creating  masked array.   
# by making  entry as invalid    
mask_arr1 = ma.masked_array(in_arr1, mask = [[ 1, 0], [ 0, 1]])   
print ("1st Masked array : ", mask_arr1)  
    
mask_arr2 = ma.masked_array(in_arr2, mask =[[ 0, 1], [ 0, 0]])   
print ("2nd Masked array : ", mask_arr2)  
    
# applying MaskedArray.dot methods   
# to masked array   
out_arr = ma.dot(mask_arr1, mask_arr2)   
print ("Dot product of two arrays : ", out_arr)       

Output:

1st Input array :  [[1 2]
 [3 4]]
2nd Input array :  [[-1 -2]
 [-3 -4]]
1st Masked array :  [[-- 2]
 [3 --]]
2nd Masked array :  [[-1 --]
 [-3 -4]]
Dot product of two arrays :  [[-6 -8]
 [-3 --]]

Code #2 :

# Python program explaining 
# numpy.MaskedArray.dot() method  
    
# importing numpy as geek   
# and numpy.ma module as ma  
import numpy as geek  
import numpy.ma as ma  
    
# creating input arrays    
in_arr1 = geek.array([[1, 2], [ 3, -1], [ 5, -3]]) 
print ("1st Input array : ", in_arr1)  
    
in_arr2 = geek.array([[1, 0, 3], [ 4, 1, 6]])  
print ("2nd Input array : ", in_arr2)  
    
      
# Now we are creating  masked array.   
# by making  entry as invalid    
mask_arr1 = ma.masked_array(in_arr1, mask = [[ 1, 0], [ 0, 1], [ 0, 0]])   
print ("1st Masked array : ", mask_arr1)  
    
mask_arr2 = ma.masked_array(in_arr2, mask =[[ 0, 0, 0], [ 0, 0, 1]])   
print ("2nd Masked array : ", mask_arr2)  
    
# applying MaskedArray.dot methods   
# to masked array   
out_arr = ma.dot(mask_arr1, mask_arr2)   
print ("Dot product of two arrays : ", out_arr)       

Output:

1st Input array :  [[ 1  2]
 [ 3 -1]
 [ 5 -3]]
2nd Input array :  [[1 0 3]
 [4 1 6]]
1st Masked array :  [[-- 2]
 [3 --]
 [5 -3]]
2nd Masked array :  [[1 0 3]
 [4 1 --]]
Dot product of two arrays :  [[8 2 --]
 [3 0 9]
 [-7 -3 15]]