R- split histogram according to factor level

Question

This is my data:

type<-rep(c(0,1),100) 
diff<-rnorm(100)
data<-data.frame(type,diff)

If I want to plot historgram of diff

Answer 1

You can use the ggplot2 package:

library(ggplot2)

ggplot(data,aes(x=diff))+geom_histogram()+facet_grid(~type)+theme_bw()

You can also put them on the same plot by "dodging" them:

ggplot(data,aes(x=diff,group=type,fill=type))+
  geom_histogram(position="dodge",binwidth=0.25)+theme_bw()

If you want them to overlap, the position has to be position="identity"

ggplot(data,aes(x=diff,group=type,fill=type))+
  geom_histogram(position="identity",alpha=0.5,binwidth=0.25)+theme_bw()

If you want them to look like it does in the first one but without the border, you have to hack it a little:

data$diff[data$type==1] <- data$diff[data$type==1] + 6

ggplot(data,aes(x=diff,group=type,fill=type))+
  geom_histogram(position="identity",alpha=0.5,binwidth=0.25)+theme_bw()+
  scale_x_continuous(breaks=c(-2:2,4:8),labels=c(-2:2,-2:2))