# Linear Regression

How does regression relate to machine learning?

Given data, we can try to find the best fit line. After we discover the best fit line, we can use it to make predictions.

Data can be any data saved from Excel into a csv format, we will use Python Pandas to load the data.

Related courses

Required modules
You shoud have a few modules installed:

```sudo pip install sklearn sudo pip install scipy sudo pip install scikit-learn```

You can choose the graphical toolkit, this line is optional:

`matplotlib.use('GTKAgg')`

We start by loading the modules, and the dataset. Without data we can’t make good predictions.

The first step is to load the dataset. The data will be loaded using Python Pandas, a data analysis module. It will be loaded into a structure known as a Panda Data Frame, which allows for each manipulation of the rows and columns.

We create two arrays: X (size) and Y (price). Intuitively we’d expect to find some correlation between price and size.

The data will be split into a trainining and test set. Once we have the test data, we can find a best fit line and make predictions.

```  import matplotlib matplotlib.use('GTKAgg')   import matplotlib.pyplot as plt import numpy as np from sklearn import datasets, linear_model import pandas as pd   # Load CSV and columns df = pd.read_csv("Housing.csv")   Y = df['price'] X = df['lotsize']   X=X.reshape(len(X),1) Y=Y.reshape(len(Y),1)   # Split the data into training/testing sets X_train = X[:-250] X_test = X[-250:]   # Split the targets into training/testing sets Y_train = Y[:-250] Y_test = Y[-250:]   # Plot outputs plt.scatter(X_test, Y_test, color='black') plt.title('Test Data') plt.xlabel('Size') plt.ylabel('Price') plt.xticks(()) plt.yticks(())   plt.show()```

Finally we plot the test data.

We have created the two datasets and have the test data on the screen. We can continue to create the best fit line:

```# Create linear regression object regr = linear_model.LinearRegression()   # Train the model using the training sets regr.fit(X_train, Y_train)   # Plot outputs plt.plot(X_test, regr.predict(X_test), color='red',linewidth=3)```

This will output the best fit line for the given test data.

To make an individual prediction using the linear regression model:

`print( str(round(regr.predict(5000))) )`

## One thought on “Linear Regression”

1. - November 29, 2017