R Plotting 2 Densities Residuals vs. Normal

Question

I want to plot the density of the residuals of a regression vs. a normal distribution.

I found some code that has the end result:

library(ggplot2)

#Sample data
dat <- data.frame(dens = c(rnorm(100), rnorm(100, 10, 5))
               , lines = rep(c("a", "b"), each = 100))
#Plot.
ggplot(dat, aes(x = dens, fill = lines)) + geom_density(alpha = 0.5)

but my code looks like:

  residuals<-Regression()$error
  normalDist<- rnorm(length(residuals), mean =  mean(residuals), sd= sd(residuals))

  dat<- data.frame(error = residuals, norm = normalDist)
  print(stack(dat))
  g<-ggplot(melt(dat), aes(x = error,  fill = lines)) + geom_density(alpha = 0.5)

I want to plot the densities of "error" and "normalDist"

I am getting the error:

Error in data.frame(x = c(1, 2, 3), fill = structure(function (x, ...)  : 
  arguments imply differing number of rows: 3, 0, 386

thank you.

Answer 1

Sorry if I misunderstand what you are planning to do, but why do you have fill = lines ? Usually, I put a color there (or a condition, but in your case lines is not defined), eg

require(ggplot2)
residuals<-jitter(rep(0,10))
normalDist<- rnorm(length(residuals), mean =  mean(residuals), sd= sd(residuals))
dat<- data.frame(error = residuals, norm = normalDist)
print(stack(dat))
ggplot(dat, aes(x = error, fill = "red")) + geom_density(alpha = 0.5)

Does this help?

Edit: I just realized, are you referring to this question: Only one of two densities is shown in ggplot2

If so, see that he defined lines as a ordinal variable in his data frame (to group the rows):

dat <- data.frame(dens = c(nEXP,nCNT),lines = rep(c("Exp","Cont")))
ggplot(dat, aes(x = dens, group=lines, fill = lines)) + geom_density(alpha = .5)