R Notebook

• Adding legend to plots using ggplot2 package

Let’s take mtcars dataset from datasets package

• Plotting the relationship between hp and mpg

library(ggplot2)

library(broom)

library(dplyr)

# Build a simple linear model between hp and mpg

m1<-lm(hp~mpg,data=mtcars)

# Predict new mpg given values below 

new_mpg = data.frame(mpg=c(23,21,30,28))

new_hp<- augment(m1,newdata=new_mpg)

new_hp1<- new_hp %>% select(mpg,.fitted) %>% mutate(type1="predicted")

new_mtcars<- mtcars %>% select(mpg,hp) %>% mutate(type1="observed") %>% bind_rows(new_hp1)

tail(new_mtcars)

# plot new predicted values in the graph along with original mpg values

ggplot(data=new_mtcars,aes(x=mpg,y=hp)) + geom_point(aes(color=factor(type1))) + geom_smooth(method="lm",col=4,se=F) + 
  geom_point(data=new_mtcars,aes(y=.fitted),color="green")+scale_color_manual(name="Type",values=c("purple","green"))