## Overview

gglm, The Grammar of Graphics for Linear Model Diagnostics, is an R package and official ggplot2 extension that creates beautiful ggplot2 diagonostic plots for linear models that are easy to use and adhere to The Grammar of Graphics. The purpose of this package is to provide a sensible alternative to using the base-R plot() function to produce diagnostic plots for linear models.

## Installation

You can now install gglm from CRAN, do so with this code:

install.packages("gglm")

Or, you can install the developmental version from GitHub:

devtools::install_github("graysonwhite/gglm")

## Examples

gglm has two main types of functions. First, the gglm() function for quickly creating the four main diagnostic plots, similar to when you call plot() on an lm type object. Second, the stat_*() functions, which produce diagnostic plots the align with The Grammar of Graphics by creating ggplot2 layers that allow for easy plotting of particular model diagnostic plots.

### Example 1: Quickly creating the four diagnostic plots with gglm()

library(gglm) # Load the package
model <- lm(mpg ~ ., data = mtcars) # Create your model

gglm(model) # Plot the four main diagnostic plots

### Example 2: Using the Grammar of Graphics with the stat_*() functions

library(ggplot2) # Need to load ggplot2

ggplot(data = model) +
stat_fitted_resid()

# We can also add layers such as themes to these ggplots and adjust features of the plot:
ggplot(data = model) +
stat_cooks_leverage(alpha = 1) +
theme_minimal()

## Functions

### For quick and easy plotting

gglm() plots the four default diagnostic plots when supplied an lm object. This function works similarly to plot.lm(), except that it displays the four diagnostic plots at once.

### Following the Grammar of Graphics

stat_normal_qq(), stat_fitted_resid(), stat_resid_hist(), stat_scale_location(), stat_cooks_leverage(), stat_cooks_obs(), and stat_resid_leverage() all are ggplot2 layers used to create individual diagnostic plots. To use these, follow Example 2.