What is Regression?:
Before knowing what is linear regression, let us get ourselves familiar with regression.
Regression is a method of modelling a target value based on independent predictors.
This method is mostly used for forecasting and finding out cause and effect relationship between variables.
Regression techniques mostly differ based on the number of independent variables and the type of relationship between the independent and dependent variables.
What is Simple Linear Regression?:
Simple linear regression is a type of regression analysis where the number of independent variables is one and there is a linear relationship between the independent(x) and dependent(y) variable.
The red line in the above graph is referred to as the best fit straight line. Based on the given data points, we try to plot a line that models the points the best. The line can be modelled based on the linear equation shown below.
y = a_0 + a_1 * x ## Linear Equation
Project | 02
Project | 02 Simple Linear Regression
# Importing the dataset
dataset = read.csv('Salary_Data.csv')
# Splitting the dataset into the Training set and Test set
# install.packages('caTools')
library(caTools)
set.seed(123)
split = sample.split(dataset$Salary, SplitRatio = 2/3)
training_set = subset(dataset, split == TRUE)
test_set = subset(dataset, split == FALSE)
# Feature Scaling
# training_set = scale(training_set)
# test_set = scale(test_set)
# Fitting Simple Linear Regression to the Training set
regressor = lm(formula = Salary ~ YearsExperience,
data = training_set)
# Predicting the Test set results
y_pred = predict(regressor, newdata = test_set)
# Visualising the Training set results
library(ggplot2)
ggplot() +
geom_point(aes(x = training_set$YearsExperience, y = training_set$Salary),
colour = 'red') +
geom_line(aes(x = training_set$YearsExperience, y = predict(regressor, newdata = training_set)),
colour = 'blue') +
ggtitle('Salary vs Experience (Training set)') +
xlab('Years of experience') +
ylab('Salary')
# Visualising the Test set results
library(ggplot2)
ggplot() +
geom_point(aes(x = test_set$YearsExperience, y = test_set$Salary),
colour = 'red') +
geom_line(aes(x = training_set$YearsExperience, y = predict(regressor, newdata = training_set)),
colour = 'blue') +
ggtitle('Salary vs Experience (Test set)') +
xlab('Years of experience') +
ylab('Salary')