# [R] ggplot2 boxplot confusion

From: Chris Friedl <cfriedalek_at_gmail.com>
Date: Tue, 26 Feb 2008 20:58:10 -0800 (PST)

Ultimately my aim is to get a plot of density faceted by 2 factors with a horizontal boxplot overlaid on each density plot in the grid to indicate summary stats. So I've been experimenting with creating boxplots and density plots. Here's some representative data.

series = c('C2','C4','C8','C10','C15','C20') ids = c('ID1','ID2','ID3')
mydata <- data.frame(SERIES=rep(cases,30),ID=rep(ids,60),VALUE=rnorm(180))

1. Using R default graphics I can create a boxplot of data independent of factors as follows: boxplot(mydata\$VALUE)

But I can't see how to do this with ggplot2. All the examples in the help show x and y aesthetics. How to boxplot a single vector? (I saw a reference to a "group" parameter in R-help somewhere but can't find it in the ggplot2 help pages. Is this a case of group = identity ?)

2. I've read the density plot help and noticed the reference to ..density.. as a means to pass density data instead of original data. But I can't seem to get a boxplot to overlay a density plot. This is what I've got so far with consequent error message:

m <- ggplot(mydata, aes(x=VALUE))
m + geom_density()+ geom_boxplot(aes(x=..density..))

Error in data.frame(..., check.names = FALSE) :   arguments imply differing number of rows: 0, 180

I've tried y=..density.., both x= and y = ..density.. and neither and all fail somehow. Problem is I don't really understand what I'm doing at this point.

So can anyone help me out with this? thanks

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