## DEV Community # Learn about Linear Regression: Theory, Examples, and Applications 💻

## Introduction: What is Linear Regression and how does it work?

Linear regression is a statistical method to make predictions. It is a type of supervised machine learning model which use statistical analysis for predicting the values as per the given data.

The main goal of linear regression is to find the line which gives the minimum mean squared error. The line represents the linear relation between independent variable(x) and dependent variable{y}.

## Evaluating types of linear regression

There are mainly three types of linear regression:

### 1. Simple linear regression

When there is only one independent variable in linear regression model is said to be simple linear regression model. In this type, there is only one weight (coeffients or slope).

### 2. Multiple linear regression

When there is more than one independent variable in linear regression model is said to be simple linear regression model. In this type, there is more than one weights.

### 3. Polynomial regression

In this type of linear regression, relation between independent and dependent variable is defined by a ploynomial function.

Other form of linear refression are ridge, lasso and Logistic Regression.

## Mathematics behind linear regression

Our main goal is to find the best line which leads to min m squared error.

In case of simple linear regression, the general equation is given by:

y = a0 + a1 * x

where y is dependent variable and x in independent variable. `a1` is slope, weight and `a0` is y intercept.

For Multiple linear regression, the equation becomes

y = a0 + a1 * x1 + a2 * x3 + ....... + an * xn

Gradient descent is an algorithm which used to minimise cost function by optimising weights and bias. In simple words, it is a algorithm which is used to find the value of x at which the f(x) is minimum.

x = x0 - η * f'(x)

### Root mean squared error

The root mean squared error is also known as residual sum of squares (RSS)
This is given by:

RSS = Σ(yi - (β0 + β1xi))^2

This method is used to find the accuracy of our model. Less will be the error more will be the accuracy.

## How to Implement Linear Regression in Machine Learning Projects

Here is the sample implimentation of linear regression in python using scikit learn library.

``````import numpy as np
import pandas as pd
from sklearn.linear_model import LinearRegression
from sklearn.model_selection import train_test_split

# load data into a Pandas DataFrame

# separate the features and target variables
X = df.drop("target", axis=1)
y = df["target"]

# split the data into training and test sets
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2)

# create a Linear Regression model
reg = LinearRegression()

# fit the model to the training data
reg.fit(X_train, y_train)

# make predictions using the test set
y_pred = reg.predict(X_test)

# calculate the MSE
error = mean_squared_error(X_test, y_test)
print("Error: ", error)
``````

`train_test_split` method is used to get the data for training the model and testing the model.

## Real-World Applications of Linear Regression in Machine Learning

Linear regression is one of the most widely used machine learning algorithms. It is used to predict the value of a dependent variable based on one or more independent variables. Linear regression can be used in a variety of predictive analytics applications, such as forecasting models for sales prediction, customer segmentation, and risk management. It can also be used to identify relationships between different variables and to detect patterns in data. In this article, we will discuss some real-world applications of linear regression in machine learning. We will look at how it can be used to make predictions about future events and how it can help businesses make better decisions.

## Conclusion: Unlocking the Power of Linear Regression for Your Machine Learning Projects

Linear regression is a powerful tool for machine learning projects. It can be used to predict outcomes, identify trends, and uncover relationships between variables. By understanding the fundamentals of linear regression and how it works, you can unlock its potential to help you build better models and make more accurate predictions. With the right data and the right techniques, linear regression can be a powerful tool for your machine learning projects.