How to combine stat_ecdf with geom_ribbon?

ggplot2, plot, r

Solution

Try this (a bit of shot in the dark):

ggplot(dat, aes(x = variable)) +
  geom_ribbon(aes(x = variable,ymin = ..y..-2,ymax = ..y..+2), stat = "ecdf",alpha=0.2) +
  geom_step(stat = "ecdf")

Ok, so that's not the same thing as what you trying to do, but it should explain what's going on. The `stat` is returning a data frame with just the original x and the computed y, so I think that's all you have to work with. i.e. `stat_ecdf` only computes the cumulative distribution function for a single x at a time.

The only other thing I can think of is the obvious, calculating the lower and upper separately, something like this:

l <- ecdf(dat$lower)
u <- ecdf(dat$upper)
v <- ecdf(dat$variable)
dat$lower1 <- l(dat$variable)
dat$upper1 <- u(dat$variable)
dat$variable1 <- v(dat$variable)

ggplot(dat,aes(x = variable)) + 
  geom_step(aes(y = variable1)) + 
  geom_ribbon(aes(ymin = upper1,ymax = lower1),alpha = 0.2)

Problem

I am trying to draw an ECDF of some data with a "confidence interval" represented via a shaded region using ggplot2. I am having trouble combining `geom_ribbon()` with `stat_ecdf()` to achieve the effect I am after. Consider the following example data: ``` set.seed(1) dat <- data.frame(variable = rlnorm(100) + 2) dat <- transform(dat, lower = variable - 2, upper = variable + 2) > head(dat) variable lower upper 1 2.534484 0.5344838 4.534484 2 3.201587 1.2015872 5.201587 3 2.433602 0.4336018 4.433602 4 6.929713 4.9297132 8.929713 5 3.390284 1.3902836 5.390284 6 2.440225 0.4402254 4.440225 ``` I am able to produce an ECDF of `variable` using ``` library("ggplot2") ggplot(dat, aes(x = variable)) + geom_step(stat = "ecdf") ``` However I am unable to use `lower` and `upper` as the `ymin` and `ymax` aesthetics of `geom_ribbon()` to superimpose the confidence interval on the plot as another layer. I have tried: ``` ggplot(dat, aes(x = variable)) + geom_ribbon(aes(ymin = lower, ymax = upper), stat = "ecdf") + geom_step(stat = "ecdf") ``` but this raises the following error ``` Error: geom_ribbon requires the following missing aesthetics: ymin, ymax ``` Is there a way to coax `geom_ribbon()` into working with `stat_ecdf()` to produce a shaded confidence interval? Or, can anyone suggest an alternative means of adding a shaded polygon defined by `lower` and `upper` as a layer to the ECDF plot?

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