geom_text writing all data on all facets

问题

I used ggplot with facet_grid and I'd like to indicate on each facet the number of observations in each facet. I follow examples provided on many sites but when I get it to write anything, it writes all four observation numbers on top of each other on all four plots.

Here the geom_text layer command: geom_text(data=ldata, aes(x=xpos, y=ypos, label=lab, size=1), group=NULL, hjust=0, parse=FALSE)

and ldata is a data frame listing the coordinates (xpos, ypos) on each plot and the number of observations (lab). It's printing the numbers in the right position on the plot, but all four are written on top of each other on all four plots. I can not figure out what I'm doing wrong.

ldata:

xpos ypos lab

1 10 1.35 378

2 10 1.35 2

3 10 1.35 50

4 10 1.35 26

回答1:

You almost have it. It is just that you need one more column in your ldata data frame which is what you will give to facet_grid. (I changed the Ypos to Inf)

Notice the role of the splitter column in ldata below, and how it is used in facet_grid

xpos <- c(10,10,10) 
ypos <- c(Inf,Inf,Inf)
lab <- c(378,2,50)
splitter <- c(1:3)
ldata <- data.frame(xpos, ypos, lab, splitter)


ggplot(mtcars) + geom_bar(aes(x=cyl)) + facet_grid(~splitter) + 
  geom_text(data=ldata, aes(x=xpos, y=ypos, 
                            label=lab, size=1), 
            vjust=2, parse=FALSE)

Which produces:

来源：https://stackoverflow.com/questions/20428902/geom-text-writing-all-data-on-all-facets