Numpy MaskedArray.dot() function | Python (original) (raw)

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 :

import numpy as geek

import numpy.ma as ma

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)

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)

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 :

import numpy as geek

import numpy.ma as ma

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)

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)

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]]

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