Theoretical numbers to superimpose on histogram

If you want superimpose the theoretical numbers at the top of an histogram based on a fitted distribution (for example, using fitdistrplus()), it is not so easy. Here is a generic function for such a purpose. It is integrated in my package HelpersMG :

modeled.hist <- function(breaks, FUN, ..., sum=1) {
  # breaks is a vector with the breaks; it can be obtained directly from hist()
  # FUN is the function to integrate the density, ex. pnorm
  # ... are the parameters of pfun
  # sum is the total numbers in the histogram; 1 for emperical frequencies
  by <- breaks[2]-breaks[1]
  xp <- c(breaks, tail(breaks, 1)+by)
  par.fun <- list(...)
  par.fun <- modifyList(list(log.p=FALSE, q=xp, lower.tail=TRUE), 
                        par.fun)
  s <- do.call(FUN, par.fun)
  # s <- pfun(xp, par.fun[1], par.fun[2], log=FALSE)
  s <- head(c(s[-1], 0)-s, length(breaks))
  return(list(x=breaks+by/2, y=s*sum))
}




n <- rnorm(100, mean=10, sd=2)
breaks <- 0:20
hist(n, breaks=breaks)

s <- modeled.hist(breaks=breaks, FUN=pnorm, mean=10, sd=2, sum=100)

points(s$x, s$y, pch=19)
lines(s$x, s$y)

n <- rlnorm(100, meanlog=2, sdlog=0.4)
b <- hist(n, ylim=c(0, 70))

s <- modeled.hist(breaks=b$breaks, FUN=plnorm, meanlog=2, sdlog=0.4, sum=100)

points(s$x, s$y, pch=19)
lines(s$x, s$y)