Create matrix from array of array
import numpy as np # 3 x 2 matrix mat1 = np.array([[1,2,3], [2,3,4]]) print(mat1) #[[1 2 3] # [2 3 4]]
Create 3 x 3 from reshape
reshape is useful to change structure of array
This is an example to make 3 x 3 from 1 dim array using arange
# 3 x 3 matrix array1 = np.arange(9).reshape(3,3) print(array1)
Get 1st row
array1 = np.arange(9).reshape(3,3) # 0 - 8 3 x 3 matrix # Get only 1 row print(array1[0, :]) # [0 1 2]
Element base multiply
array1 = np.arange(9).reshape(3,3) # 3 x 3 array2 = np.arange(9, 18).reshape(3, 3) # 3 x 3 print(array1 * array2) # multiply each element
Inner Product
array1 = np.arange(9).reshape(3,3) # 3 x 3 array2 = np.arange(9, 18).reshape(3, 3) # 3 x 3 print(np.dot(array1, array2))
Create Identity matrix
d = np.identity(4) print(d) ''' [[ 1. 0. 0. 0.] [ 0. 1. 0. 0.] [ 0. 0. 1. 0.] [ 0. 0. 0. 1.]] '''
Create zero martix
a = np.zeros((3, 3)) print(a) ''' [[ 0. 0. 0.] [ 0. 0. 0.] [ 0. 0. 0.]] '''
Create one matrix (all elements are one)
b = np.ones((3, 4)) print(b) ''' [[ 1. 1. 1. 1.] [ 1. 1. 1. 1.] [ 1. 1. 1. 1.]] '''
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