[R] plotting dnorm() issued from mclust models

[Frederic Jean]

Dear all

I have a problem in fitting lines() of the normal distributions  
identified with Mclust on a histogram or a mclust1Dplot. Here is some  
sample code to explain :

  set.seed(22)
  foo <- c(rnorm(400, 10, 2), rnorm(500, 17, 4))
  mcl <- Mclust(foo, G=2)
  mcl.sd <- sqrt(mcl$parameters$variance$sigmasq)
  mcl.size <- c(length(mcl$classification[mcl$classification==2]),  
length(mcl$classification[mcl$classification==1]))
  x <- pretty(c(0:44), 100)

  #### my plot of histogram and lines of normal distributions
  #### SEEMS OK (or am I wrong ?) using frequencies :
  histA <- hist(foo, breaks =c(0:44), ylim = c(0,100))
  lines(x, dnorm(x, mcl$parameters$mean[1], mcl.sd[1])*mcl.size[1],  
col =2, lw=2)
  lines(x, dnorm(x, mcl$parameters$mean[2], mcl.sd[2])*mcl.size[2],  
col =2, lw=2)

  #### my plot of histogram and lines of normal distributions
  #### IS wrong when using prob :
  mclust1Dplot(foo, parameters = mcl$parameters, z = mcl$z, what = "density")
  histA <- hist(foo, breaks =c(0:44), prob = T, add =T)
  lines(x, dnorm(x, mcl$parameters$mean[2], mcl.sd[2]), col =2, lw=2)
  lines(x, dnorm(x, mcl$parameters$mean[1], mcl.sd[1]), col =2, lw=2)

In second plot, the bell shaped curves are obviously too high and it  
seems that I miss something obvious in scaling dnorm()'s in building  
the second plot: I tried different things like scaling dnorm() by the  
proportion of individuals belonging to cluster 1 and 2 respectively,  
but with no success.

Could someone help to point my errors ?
Many thanks in advance

Fred J.