bytesinflight bytesinflight - 2 months ago 19
R Question

Apply a ggplot-function per group with dplyr and set title per group

I would like to create one separate plot per group in a data frame and include the group in the title.

With the iris dataset I can in base R and ggplot do this

plots1 <- lapply(split(iris, iris$Species),
function(x)
ggplot(x, aes(x=Petal.Width, y=Petal.Length)) +
geom_point() +
ggtitle(x$Species[1]))


Is there an equivalent using dplyr?

Here's an attempt using facets instead of title.

p <- ggplot(data=iris, aes(x=Petal.Width, y=Petal.Length)) + geom_point()
plots2 = iris %>% group_by(Species) %>% do(plots = p %+% . + facet_wrap(~Species))


where I use %+% to replace the dataset in p with the subset for each call.

Workaround with facets

or (working but complex) with ggtitle

plots3 = iris %>%
group_by(Species) %>%
do(
plots = ggplot(data=.) +
geom_point(aes(x=Petal.Width, y=Petal.Length)) +
ggtitle(. %>% select(Species) %>% mutate(Species=as.character(Species)) %>% head(1) %>% as.character()))


Working example

The problem is that I can't seem to set the title per group with ggtitle in a very simple way.

Thanks!

Answer

Use .$Species to pull the species data into ggtitle:

iris %>% group_by(Species) %>% do(plots=ggplot(data=.) +
         aes(x=Petal.Width, y=Petal.Length) + geom_point() + ggtitle(unique(.$Species)))