r - Add text to ggplot with facetted densities -

i'm encountering problem when trying make density plot ggplot. data bit in example here.

require(ggplot2) require(plyr) mms <- data.frame(deliciousness = rnorm(100),                   type=sample(as.factor(c("peanut", "regular")), 100, replace=true),                   color=sample(as.factor(c("red", "green", "yellow", "brown")), 100, replace=true))   mms.cor <- ddply(.data=mms, .(type, color), summarize, n=paste("n =", length(deliciousness)))  plot <- ggplot(data=mms, aes(x=deliciousness)) + geom_density() + facet_grid(type ~ color) + geom_text(data=mms.cor, aes(x=1.8, y=5, label=n), colour="black", inherit.aes=false, parse=false) 

labelling each facet labels work quite unless scales each facet vary. have idea how achieve putting labels @ same location when scales per facet differ?

best, daniel

something this?

plot <- ggplot(data=mms, aes(x=deliciousness)) +   geom_density(aes(y=..scaled..)) + facet_grid(type ~ color) +   geom_text(data=mms.cor, aes(x=1.2, y=1.2, label=n), colour="black") plot 

there way limits set internally ggplot scales="free", involves hacking grob (graphics object). since seem want density plots have equal height (???), can aes(y=..scaled...). setting location labels straightforward.

edit (response op's comment)

this meant hacking grob. note takes advantage of internal structure used gglpot. problem change @ time new version (and in fact different older versions). there no guarantee code work in future.

plot <- ggplot(data=mms, aes(x=deliciousness)) +   geom_density() +    facet_grid(type ~ color, scales="free") panels <- ggplot_build(plot)[["panel"]] limits <- do.call(rbind,lapply(panels$ranges,                                function(range)c(range$x.range,range$y.range))) colnames(limits) <- c("x.lo","x.hi","y.lo","y.hi") mms.cor <- cbind(mms.cor,limits) plot +    geom_text(data=mms.cor, aes(x=x.hi, y=y.hi, label=n), hjust=1,colour="black") 

the basic idea generate plot without text, build graphics object using ggplot_build(plot). can extract x- , y-limits, , bind labels in mms.cor data frame. render plot text, using these limits.

note plots different earlier answer because did not use set.seed(...) in code generate dataset (and forgot add it...).