Add car type column to mtcars built-in R dataset. Add subgroups of cars based on mpg.
mtcars$type=row.names(mtcars)
mtcars$mpg_breaks=cut(mtcars$mpg,breaks=c(
0,20,30,40),labels=c("0-20mpg","20-30mpg","30-40mpg"));head(mtcars)
## mpg cyl disp hp drat wt qsec vs am gear carb
## Mazda RX4 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
## Mazda RX4 Wag 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
## Datsun 710 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
## Hornet 4 Drive 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
## Hornet Sportabout 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
## Valiant 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
## type mpg_breaks
## Mazda RX4 Mazda RX4 20-30mpg
## Mazda RX4 Wag Mazda RX4 Wag 20-30mpg
## Datsun 710 Datsun 710 20-30mpg
## Hornet 4 Drive Hornet 4 Drive 20-30mpg
## Hornet Sportabout Hornet Sportabout 0-20mpg
## Valiant Valiant 0-20mpg
Plot car types by mpg and cylinder
library(ggplot2)
q=qplot(type,data=mtcars,geom="bar",weight=mpg,fill=cyl,ylab="MPG",xlab="Car manufacturer and model",main="Cars described by miles per gallon and number of cylinders")
q+facet_wrap(~mpg_breaks, scale="free",ncol=1)+theme(axis.text.x=element_text(angle=90))