Calculate the mean of a row or column, and use the dot multiplication on matrices.
Mean and dot

Mean and dot

In [1]:
import numpy as np

In [4]:
# create 3 x 1 array
lst = [[6], [7], [8]]
array = np.array(lst)
array

Out[4]:
array([[6],
[7],
[8]])
In [3]:
# create 1 x 3 array
lst_2 = [[2, 2, 2]]
array_2 = np.array(lst_2)
array_2

Out[3]:
array([[2, 2, 2]])
In [5]:
# np.mean(array_name)
# it simply sums up all elements and divide the sum by the number of elements
# this will output a single number
np.mean(array)

Out[5]:
7.0
In [6]:
# np.mean(array_name)
np.mean(array_2)

Out[6]:
2.0
In [9]:
# dot is different from element-wise multiplication

# 3 x 1 dot 1 x 3
# this would output a 3 x 3 array
np.dot(array, array_2)

Out[9]:
array([[12, 12, 12],
[14, 14, 14],
[16, 16, 16]])
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