inner

Description

Calculate the inner product of two arrays. It returns the ordinary inner product of vectors for 1-D arrays (without complex conjugation), and returns a sum product over the last axes for arrays in higher dimensions.

Mandatory Input Parameters

Parameter	Type	Description
a	array_like	The first argument.
b	array_like	The second argument.

Note that if a and b are nonscalar, their last dimensions must match. Otherwise, an exception is raised.

Optional Input Parameters

None

Return Value

Type	Description
ndarray	Returns the inner product of a and b. If a and b are both scalars or both 1-D arrays, a scalar is returned; otherwise an array is returned.

Examples

>>> import numpy as np
>>> a = np.array([1,2,3])
>>> b = np.array([0,1,2])
>>> np.inner(a, b)
8
>>> 
>>> a = np.arange(24).reshape((2,3,4))
>>> a
array([[[ 0,  1,  2,  3],
        [ 4,  5,  6,  7],
        [ 8,  9, 10, 11]],

       [[12, 13, 14, 15],
        [16, 17, 18, 19],
        [20, 21, 22, 23]]])
>>> b = np.arange(4)
>>> b
array([0, 1, 2, 3])
>>> np.inner(a, b)
array([[ 14,  38,  62],
       [ 86, 110, 134]])
>>> 
>>> a = np.arange(2).reshape((1,1,2))
>>> b = np.arange(6).reshape((3,2))
>>> np.inner(a, b)
array([[[1, 3, 5]]])
>>> 
>>> a = np.eye(2)
>>> a
array([[1., 0.],
       [0., 1.]])
>>> np.inner(a, 5)
array([[5., 0.],
       [0., 5.]])
>>>

Parent topic: Basic Statistics Functions