making a frequency polygon with the y axis as a percentage of the max

Question

given the code

set.seed(1234)
dat <- data.frame(cond = factor(rep(c("A","B"), each=200)), 
                  rating = c(rnorm(200),rnorm(200, mean=.8)))
head(dat)
ggplot(dat, aes(x=rating)) + geom_freqpoly()

I need to change the y-axis to percentage of the maximum count. What is the best approach?

Further edited: I am not looking for a way to show the percentage of the total data points, but to set the maximum count as 100%, and show all the other bins as a percentage of that max. So the y axis would run from 1-100, with the top of the peak at 100.

Answer 1

I was a bit confused as to what you were asking initially, but now I understand: you want to represent the y-axis "normalized" to ..count.., where your highest point is equal to 1.0 (maximum value), and all other points are equal value / maximum value.

For that, this should work:

ggplot(dat, aes(x=rating, y=..count../max(count))) + geom_freqpoly()

If you want to change the values to be from 0 to 100 (instead of 0 to 1), then just multiply by 100:

ggplot(dat, aes(x=rating, y=(..count../max(count))*100)) + geom_freqpoly()