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@chtmorris
Last active May 1, 2021 23:42
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Classwork matrix and vector multiplication
import numpy as np
# Define matrix and vector
vector = [1, 2, 3, 4]
matrix = [ [1, 2, 3, 4],
[5, 6, 7, 8],
[9, 0, 1, 2] ]
# Function 1
def vectorMatrixMultiplication(matrix,vector):
"""
Iterate over matrix rows with for loop
Set an answer variable
For each vector, multiply vector by corresponding matrix integer in row
Sum the resulting 4 outputs of the row
Set answer equal to output
"""
answerList = []
for x in range(len(matrix)):
answer = 0
for y in range(len(vector)):
answer = answer + vector[y] * matrix[x][y]
answerList.append(answer)
print answerList
# Function 2
def matrixMutiplication(matrix1, matrix2):
"""
Same methodology as above
One additional loop required to iterate over the second matrix rows
"""
answerMatrix=[]
for x in range(len(matrix1)):
answerList = []
for y in range(len(matrix2)):
answer = 0
for z in range(len(matrix2[y])):
answer = answer + matrix2[y][z] * matrix2[x][z]
answerList.append(answer)
answerMatrix.append(answerList)
print np.matrix(answerMatrix)
# Call functions
vectorMatrixMultiplication(matrix,vector)
matrixMutiplication(matrix, matrix)
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