ggplot2: Splitting facet/strip text into two lines

问题

Consider the following ggplot2 graph with long facet/strip text broken in two lines. The text goes outside the area devoted to facet titles.

library(ggplot2)
x <- c(1:3, 1:3)
y <- c(3:1, 1:3)
grp <- c(0, 0, 0, 1, 1, 1)
p <- qplot(x=x, y=y) + geom_line() + facet_wrap(~ grp)
grob <- ggplotGrob(p)
strip.elem.y <- grid.ls(getGrob(grob, "strip.text.x", 
                grep=TRUE, global=TRUE))$name
grob <- geditGrob(grob, strip.elem.y[1], 
        label="First line and\n second line" )
grid.draw(grob)

Is there a way to increase the height of the strip text area ?

回答1:

I tried this a variety of ways but was frustrated getting the paste(strwrap(text, width=40), collapse=" \n") to give me results for the single row of data and not concatenate the each bit of text from the entire list.

I came up with a solution that worked best for me. I wrote a function like the one below. Given a dataframe data with column text

wrapit <- function(text) {
  wtext <- paste(strwrap(text,width=40),collapse=" \n ")
  return(wtext)
}

data$wrapped_text <- llply(data$text, wrapit)
data$wrapped_text <- unlist(data$wrapped_text)

After I called this function, I just applied my labeller function to the wrapped_text column instead of the text column.

回答2:

ggplot2 supports a built in way of doing this using label_wrap_gen.

x <- c(1:3, 1:3)
y <- c(3:1, 1:3)
grp = c(rep("group 1 with a long name",3),rep("group 2 with a long name",3))
d = data.frame(x = x, y =y, grp = grp)
ggplot(d, aes(x=x,y=y)) + geom_line() + facet_wrap(~ grp, labeller = label_wrap_gen(width=10))

回答3:

You can use a 2-line label:

grp <- c(rep("foo\nbar",3), 1, 1, 1)
qplot(x=x, y=y) + geom_line() + facet_wrap(~ grp)

来源：https://stackoverflow.com/questions/9052650/ggplot2-splitting-facet-strip-text-into-two-lines