An Introduction to Simple Linear Regression in R

Introduction

The goal is to introduce linear regression in R by solving the Kaggle Ames Housing competition.

Don’t expect a great score. There’s a lot more to learn but this blog will take you from zero to submission.

Simple linear regression only uses one variable/predictor/feature to make a prediction. In our case, the feature is the ground living area: GrLivArea. We chose this parameter by reading this document.

The R code can be found on Github

Load a couple libraries

library(tidyverse) # A lot of magic in here
library(GGally)

Read the training data

train <- read_csv("../input/train.csv")

## 
## ── Column specification ────────────────────────────────────────────────────────
## cols(
##   .default = col_character(),
##   Id = col_double(),
##   MSSubClass = col_double(),
##   LotFrontage = col_double(),
##   LotArea = col_double(),
##   OverallQual = col_double(),
##   OverallCond = col_double(),
##   YearBuilt = col_double(),
##   YearRemodAdd = col_double(),
##   MasVnrArea = col_double(),
##   BsmtFinSF1 = col_double(),
##   BsmtFinSF2 = col_double(),
##   BsmtUnfSF = col_double(),
##   TotalBsmtSF = col_double(),
##   `1stFlrSF` = col_double(),
##   `2ndFlrSF` = col_double(),
##   LowQualFinSF = col_double(),
##   GrLivArea = col_double(),
##   BsmtFullBath = col_double(),
##   BsmtHalfBath = col_double(),
##   FullBath = col_double()
##   # ... with 18 more columns
## )
## ℹ Use `spec()` for the full column specifications.

Read test data

test <- read_csv("../input/test.csv")

## 
## ── Column specification ────────────────────────────────────────────────────────
## cols(
##   .default = col_character(),
##   Id = col_double(),
##   MSSubClass = col_double(),
##   LotFrontage = col_double(),
##   LotArea = col_double(),
##   OverallQual = col_double(),
##   OverallCond = col_double(),
##   YearBuilt = col_double(),
##   YearRemodAdd = col_double(),
##   MasVnrArea = col_double(),
##   BsmtFinSF1 = col_double(),
##   BsmtFinSF2 = col_double(),
##   BsmtUnfSF = col_double(),
##   TotalBsmtSF = col_double(),
##   `1stFlrSF` = col_double(),
##   `2ndFlrSF` = col_double(),
##   LowQualFinSF = col_double(),
##   GrLivArea = col_double(),
##   BsmtFullBath = col_double(),
##   BsmtHalfBath = col_double(),
##   FullBath = col_double()
##   # ... with 17 more columns
## )
## ℹ Use `spec()` for the full column specifications.

Keep only a subset of the data

train <- select(train, c("Id", "GrLivArea", "LotArea", "TotalBsmtSF", "YearBuilt", "SalePrice")) # Tidyverse
test <- select(test, c("Id", "GrLivArea", "LotArea", "TotalBsmtSF", "YearBuilt")) # Tidyverse

Correlation Plot

ggpairs(train, binwidth=30)

## Warning in warn_if_args_exist(list(...)): Extra arguments: 'binwidth' are being
## ignored. If these are meant to be aesthetics, submit them using the 'mapping'
## variable within ggpairs with ggplot2::aes or ggplot2::aes_string.