Numpy Element-wise In Operation

Suppose I have a column vector y with length n, and I have a matrix X of size n*m. I want to check for each element i in y, whether the element is in the corresponding row in X. Wh

Solution 1:

Vectorized approach using broadcasting -

((X == y[:,None]).any(1)).astype(int)

Sample run -

In [41]: X        # Input 1Out[41]: 
array([[1, 2, 3],
       [3, 4, 5],
       [4, 3, 2],
       [2, 2, 2]])

In [42]: y        # Input 2Out[42]: array([1, 2, 3, 4])

In [43]: X == y[:,None] # Broadcasted  comparison
Out[43]: 
array([[ True, False, False],
       [False, False, False],
       [False,  True, False],
       [False, False, False]], dtype=bool)

In [44]: (X == y[:,None]).any(1) # Checkforanymatch along eachrowOut[44]: array([ True, False,  True, False], dtype=bool)

In [45]: ((X == y[:,None]).any(1)).astype(int) # Convertto1s and0s
Out[45]: array([1, 0, 1, 0])