matrix multiplication

matrixmultiplication.py

"""
Created on Wed Apr 10 13:27:17 2019

@author: jenncross
"""

import numpy as np




#Apples cost $3, oranges cost $4, grapes cost $2
# .... Boston prices, am I right?
prices = np.array([[3],
                   [4],
                   [2]])


#On monday we sell 13 apples, 8 oranges, 6 grapes?
#On tuesday we sell 9, 7, and 4
#On wednesday 7, 4, 0
#On thursday 15, 6, 3

sales = np.array([[13, 8, 6],
                  [9, 7, 4],
                  [7, 4, 0],
                  [15, 6, 3]])
        
     
#How much to we make each day?       
income = np.matmul(sales, prices)

print(income)


#What if we wanted to make $100 monday, $75 tuesday, and  $50 wednesday?
# This would be a system of equations.
# 13*a + 8*o + 6*g = 100
# 9*a + 7*o + 4*g = 75
# 7*a + 4*o + 0*g = 50
# What are the prices a, o and g that make this work?

sales = np.array([[13, 8, 6],
                  [9, 7, 4],
                  [7, 4, 0]])

goals = np.array([[100],
                  [75],
                  [50]])

#We can solve this system of equations with numpy matrices ....
solution_prices = np.linalg.solve(sales, goals)

print(solution_prices)