Reputation:
Here is a piece of ggplot2 code plotting a set of 4 densities from samples:
library('reshape')
library('ggplot2')
data <- matrix(0,5,100)
for(i in seq(1,5,1)){
data[i,] <- rnorm(100,i,1)
}
df <- data.frame(melt(data))
g <- ggplot(data=df, aes(x=value,group=X1)) +
geom_density(fill="blue",alpha=0.5)
g
I would like to add the "index" of the density at the top of each of them. I tried many things including:
g + geom_text(aes(label=X1,y=0.5,group=X1));
Which does not give me what I expect but the index of the densities for each sample (as it was ignoring the "group" argument). I am surely missing something but what?
Upvotes: 0
Views: 4035
Reputation: 81753
The problem is: ggplot
prints the label for each data point. You first need to calculate the center of the distributions:
df2 <- aggregate(value ~ X1, df, function(x) mean(range(x))/2)
This returns the center for each X1
group. Then, the new data frame, df2
can be used with the geom_text
function:
ggplot(data = df,aes(x = value, group = X1))+
geom_density(fill = "blue", alpha = 0.5) +
geom_text(data = df2, aes(label = X1, y = 0.5))
Alternatively, you could calculate the positions of the densities' peaks:
df2 <- aggregate(value ~ X1, df, function(x) {
dens <- density(x)
return(dens$x[which.max(dens$y)])
})
Upvotes: 6