geom_violin

[Winston Chang]

Hi everyone - I have a rough working version of geom_violin. Comments and suggestions are appreciated.

https://github.com/wch/ggplot2/tree/feature/violin

Some examples -- hopefully these inline images will show up properly...

set.seed(110)

dat <- data.frame(x=LETTERS[1:3], y=round(rnorm(90),2))

# With points overlaid

ggplot(dat, aes(x=x, y=y)) + geom_violin() + geom_point(shape=21)

# Narrower, no points

ggplot(dat, aes(x=x, y=y)) + geom_violin(width=.5)

# Narrower, with tails

ggplot(dat, aes(x=x, y=y)) + geom_violin(width=.5, trim=FALSE) + geom_point(shape=21)

# With box plot

ggplot(dat, aes(x=x, y=y)) + geom_violin(width=.5) + geom_boxplot(width=.1, outlier.size=0)

# Dodging works

ggplot(dat, aes(x="foo", y=y, fill=x)) + geom_violin()

[Dennis Murphy]

Nice. An example with point jitter would be good, too; something like

ggplot(dat, aes(x=x, y=y)) + geom_violin() +

     geom_point(shape=21, position = position_jitter(width = 0.2))

That's a common problem in strip chart/boxplot combinations - it would be comforting to know that jittering works in geom_violin() too. I haven't tried it out yet, but I will when it gets merged into ggplot2. Just a wish list item :)

Dennis

[Winston Chang]

Dennis, thanks for the feedback. Here's an example with jitter:

ggplot(dat, aes(x=x, y=y)) + geom_violin() + 

    geom_point(shape=21, position=position_jitter(height=0, width=.2))

I think the next thing I'm going to do is implement a Wilkinson-style dot plot. I posted some code on the main ggplot2 list a little while back to make make this kind of graph, but it wasn't very elegant -- it required using a continuous x axis. Here's what it looks like using that hack:

I think this is way more informative than jittering. I just have to figure out a good way to do it. It's kind of complicated because of the way dot size is related to the binning and axis dimensions. With "regular" point graphs, the dot diameter is independent of the axis dimensions, but with a Wilkinson-style dot plot, the dot diameter determines the bin size.

I'm hoping that I can use geom_point with a new position_xx and/or stat_xx, but if not, I'll have to make a new geom.

-Winston

[Hadley Wickham]

Looks very cool, thanks!

Hadley

--
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/

[Carey Duryea]

so geom_violin is for compariing densities of distrobutions next to eachother?