In this recipe, we will learn how to split a variable at arbitrary intervals of our choice to compare the box plots of values within each interval.
We will continue using the base graphics library functions, so we need not load any additional library or package. We just need to run the recipe code at the R prompt. We can also save the code as a script to use it later. Here, we will use the metals.csv example dataset again:
metals<-read.csv("metals.csv")Let's make a box plot of copper (Cu) concentrations split at values 0, 40, and 80:
cuts<-c(0,40,80)
Y<-split(x=metals$Cu, f=findInterval(metals$Cu, cuts))
boxplot(Y,xaxt="n",
border = "white",col = "black",boxwex = 0.3,
medlwd=1,whiskcol="black",staplecol="black",
outcol="red",cex=0.3,outpch=19,
main="Summary of Copper concentrations",
xlab="Concentration ranges",las=1)
axis(1,at=1:length(clabels),
labels=c("Below 0","0 to 40","40 to 80","Above 80")...