Force R to plot histogram as probability (relative frequency)

Question

I am having trouble plotting a histogram as a pdf (probability)

I want the sum of all the pieces to equal an area of one so it\'s easier to compare across datasets. For

Answer 1

To answer the request to plot probabilities rather than densities:

h <- hist(vec, breaks = 100, plot=FALSE)
h$counts=h$counts/sum(h$counts)
plot(h)