Question

Is there any way to plot the cumulative probability from a frequency table? I mean a “smooth” version of it, similar to the way geom_density() plots.

So far, I managed to plot the individually calculated probabilities as points joined by lines, but it doesn’t look very good.

Answer 1

I generate some test data:

set.seed(1)
x <- sort(sample(1:100, 20))
p <- runif(x); p <- cumsum(p)/sum(p)
table <- data.frame(x=x, prob=p)

You can use geom_smooth from the ggplot2 package.

require("ggplot2")
qplot(x=x, y=p, data=table, aes(ymin=0, ymax=1)) + ylab("ecf") + 
geom_smooth(se=F, stat="smooth", method="loess", fullrange=T, fill="lightgrey", size=1)

As an alternative, an easy way to specifiy smoothing by a parameter try DeconCdf from the decon package:

require("decon")
plot(DeconCdf(x, sig=1))

If you want to use ggplot, you first have to transform the Decon function object in a data.frame.

f <- DeconCdf(x, sig=1)
m <- ggplot(data=data.frame(x=f$x, p=f$y), aes(x=x, y=p, ymin=0, ymax=1)) + ylab("ecf")
m + geom_line(size=1)

Use the sig-Parameter as your smoothing parameter:

f <- DeconCdf(x, sig=0.3)
m <- ggplot(data=data.frame(x=f$x, p=f$y), aes(x=x, y=p, ymin=0, ymax=1)) + ylab("ecf")
m + geom_line(size=1)