如何在没有数据框的情况下在 ggplot2 中创建直方图？

Question

I am plotting two histograms in R by using the following code.

x1<-rnorm(100)
x2<-rnorm(50)  
h1<-hist(x1)
h2<-hist(x2)
plot(h1, col=rgb(0,0,1,.25), xlim=c(-4,4), ylim=c(0,0.6), main="", xlab="Index", ylab="Percent",freq = FALSE)
plot(h2, col=rgb(1,0,0,.25), xlim=c(-4,4), ylim=c(0,0.6), main="", xlab="Index", ylab="Percent",freq = FALSE,add=TRUE)
legend("topright", c("H1", "H2"), fill=c(rgb(0,0,1,.25),rgb(1,0,0,.25)))

The code produces the following output.

I need a visually good looking (or stylistic) version of the above plot. I want to use ggplot2. I am looking for something like this (see Change fill colors section) . However, I think, ggplot2 only works with data frames. I do not have data frames in this case. Hence, how can I create good looking histogram plot in ggplot2? Please let me know. Thanks in advance.

Answer 1

You can (and should) put your data into a data.frame if you want to use ggplot . Ideally for ggplot , the data.frame should be in long format. Here's a simple example:

df1 = rbind(data.frame(grp='x1', x=x1), data.frame(grp='x2', x=x2))

ggplot(df1, aes(x, fill=grp)) + 
  geom_histogram(color='black', alpha=0.5)

There are lots of options to change the appearnce how you like. If you want to have the histograms stacked or grouped, or shown as percent versus count, or as densities etc., you will find many resources in previous questions showing how to implement each of those options.