Question

I am a beginner in R.

I am working on creating a relative frequency histogram (from random uniform numbers with 1,000 samples of 2) with a normal curve over-layed on top.

So far this is my attempt at the code:

set.seed(32423432)
x1 <-runif(2000,0,1)
m<-matrix(x1,ncol=2)
msum<-apply(m,1,sum)
bins=seq(-4,4,by=.2)
msum2<-msum/2
msum2<-msum2-(1/2)
msum2<-msum2*sqrt(2)
hist(msum2,breaks=bins, freq= FALSE, right=FALSE)

I have a few problems with this:

1. the percentage on the y-axis makes no sense to me (I would expect to see something between 0 and .5)
2. I should see way more bins
3. I have no idea how to change the x-axis labels to every .4
4. I cannot seem to get a normal curve on top of this histogram

Answer 1

1. Density sums to one over the whole plot (note that your interval sizes are less than 1).
   See ?hist “If all(diff(breaks) == 1), they are the relative frequencies counts/n”

2. You would see more bins if msum2 had a greater range

   range(msum2)
   [1] -0.6918129 0.6795006

   hist(c(1,1,3,3 -3.5,-3.5, msum2),breaks=bins, freq= FALSE, right=FALSE)

3.

hist(msum2,breaks=bins, freq= FALSE, right=FALSE, xaxt="n")
axis(1,at=bins,labels=bins)

4 . Normal curve

x <- seq(-4, 4, length=100)

`lines(x,dnorm(x))`