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• Lab
• A Cloud Guru

# Creating a Matrix Using NumPy Arrays

If you're in the position where your work requires you to work with n-dimensional arrays (matrices), then `numpy` will be a staple tool in your toolbelt. Knowing how to create matrices using arrays is a fundamental skill for working with `numpy`. In this hands-on lab, we go through the process of installing `numpy`, building up some arrays, and combining them to create a matrix. To feel comfortable completing this lab, you'll want to know how to do the following: - Using NumPy arrays. Watch the "What are NumPy Arrays?" video from the [Using Python's Math, Science, and Engineering Libraries](https://linuxacademy.com/cp/modules/view/id/62) course. - Using NumPy matrices. Watch the "Reshaping a NumPy Array into a Matrix" video from the [Using Python's Math, Science, and Engineering Libraries](https://linuxacademy.com/cp/modules/view/id/621) course.

## Path Info

Level
Intermediate
Duration
30m
Published
Aug 21, 2020

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1. Challenge

### Install NumPy

Before we can start working with NumPy, we'll need to make sure that we have it installed. Utilize pip to install the numpy package.

2. Challenge

### Creating NumPy Arrays for Each Store's Sales and Item Prices

Since we have the sales numbers for each item from each store, we can create an array for each store's sales that can later be used to make calculations. We need to make sure that we're putting the sales numbers for each item in the same position for each of our stores' arrays. Create a 4 item array for each store, placing the number of sales for each item in the order of pens, notebooks, staplers, and backpacks.

3. Challenge

### Create the Sales and Prices Matrix

Because we have 4 different items, each stores' sales are stored as a 4 item, one-dimensional array, or a 1x4 matrix. We can use matrix multiplication to calculate the revenue for a store by multiplying that array with a 4x1 matrix where each row is the price for the corresponding column item in the sales arrays. Combine all of our sales variables into a single 4x4 matrix so that we can calculate the revenue for all of the stores at the same time, and create a 4x1 prices matrix that has the prices list from top to bottom for pen, notebook, stapler, and backpack.

4. Challenge

### Calculate Store Revenues and Total Revenue

Calculate the dot product of these two matrices to get the revenue for each store and then utilize those values to calculate the total revenue.

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## What's a lab?

Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.

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### Guided walkthrough

Follow along with the author’s guided walkthrough and build something new in your provided environment!

### Did you know?

On average, you retain 75% more of your learning if you get time for practice.