I have two sets of data formed as follows:
A = {id1: 0.3, id2: 0.1, id3: 0.3 ... idn: 0.2}
B = {id1: 0.01, id2: 0.04, id3: 0.75 ... idn: 0.9}
I used the ggplot function of R to plot the density values in the same graph, thus:
Iwonderwhattheid'sthatareonthepeaksofeachdensityare.Forexample,whataretheid'sthatareinthepeak(inred)ofeachdensity? 
I would like to know if the id's are different or equal in the peaks, ie in the high density values.
You can get the data from the graph generated by ggplot2 by explicitly requesting print .
For example, let's generate a histogram:
rm(list = ls())
library(ggplot2)
set.seed(10)
df <- data.frame(x = rnorm(10000))
grafico <- ggplot(df, aes(x = x)) + geom_density()
grafico
Togetthedataofthegraphandthustoknowwhatthemaximumvalueaskstheprintexplicitly,savethedataandseethemaximumvalueofthedensity:
dados_grafico<-print(grafico)$data[[1]]dados_grafico[which.max(dados_grafico$density),c("x","density")]
x density
238 -0.1253751 0.3963933
In this case the maximum occurs at x = -0.1253751 with density of 0.3963933.