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 :

Python3

# 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 :

Python3

# 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]]