Overlapping stacked density plots - r

Question

I'm trying to achieve a similar plot to this one, using R's native plot command.
I was able to get something similar with the code below, however, I'd like the density polygons to overlap. Can anyone suggest a way to do this?
data = lapply(1:5, function(x) density(rnorm(100, mean = x)))
par(mfrow=c(5,1))
for(i in 1:length(data)){
plot(data[[i]], xaxt='n', yaxt='n', main='', xlim=c(-2, 8), xlab='', ylab='', bty='n', lwd=1)
polygon(data[[i]], col=rgb(0,0,0,.4), border=NA)
abline(h=0, lwd=0.5)
}
Outputs:

Answer 1

I would do it something like the following. I plot the densities in the same plot but add an integer to the y values. To make them overlapping i multiply by a constant factor fac.
# Create your toy data
data <- lapply(1:5, function(x) density(rnorm(100, mean = x)))
fac <- 5 # A factor to make the densities overlap
# We make a empty plot
plot(1, type = "n", xlim = c(-3, 10), ylim = c(1, length(data) + 2),
axes = FALSE, xlab = "", ylab = "")
# Add each density, shifted by i and scaled by fac
for(i in 1:length(data)){
lines( data[[i]]$x, fac*data[[i]]$y + i)
polygon(data[[i]]$x, fac*data[[i]]$y + i, col = rgb(0, 0, 0, 0.4), border = NA)
abline(h = i, lwd = 0.5)
}

Answer 2

(Note: This content was previously edited into the Question and was written by #by0.)
Thanks to #AEBilgrau, I quickly put together this function which works really nicely. Note: you need to play around with the factor fac depending on your data.
stacked.density <- function(data, fac = 3, xlim, col = 'black',
alpha = 0.4, show.xaxis = T,
xlab = '', ylab = ''){
xvals = unlist(lapply(data, function(d) d$x))
if(missing(xlim)) xlim=c(min(xvals), max(xvals))
col = sapply(col, col2alpha, alpha)
if(length(col) == 1) col = rep(col, length(data))
plot(1, type = "n", xlim = xlim, ylim = c(1,length(data) + 2),
yaxt='n', bty='n', xaxt=ifelse(show.xaxis, 'l', 'n'), xlab = xlab, ylab = ylab)
z = length(data):1
for(i in 1:length(data)){
d = data[[ z[i] ]]
lines(d$x, fac*d$y + i, lwd=1)
polygon(d$x, fac*d$y+ i, col=col[i], border=NA)
abline(h = i, lwd=0.5)
}
}
data <- lapply(1:5, function(x) density(rnorm(100, mean = x)))
stacked.density(data, col=c('red', 'purple', 'blue', 'green', 'yellow'), alpha=0.3, show.xaxis=T)
outputs: