Adjusting size of plot in R

I have a distribution plot that I want like this:

dev.new(width=5,height=2)
plot(w.count.v, main="Distribution Plot of 'she' in Two Kinds",xlab="Novel Time",ylab=m=c(0,1),yaxt="n")

How do I save it as a .png as the size on the device? When I save it, this is the resulting image.