Filling cross over under a Cumulative Frequency plot using ggplot in R

Question

I am trying to plot two Cumulative Frequency curves in ggplot, and shade the cross over at a certain cut off. I haven't been using ggplot for long, so I was hoping someone might be able to help me with this one.

The plot without filled regions, looks like this...

Which I have created using the following code...

library(ggplot2) # required 

north <- rnorm(3060, mean=277,sd=3.01) # to create synthetic data 
south <- rnorm(3060, mean=278, sd=3.26) # in place of my real data. 

#placing in dataframe
df_temp <- data.frame(temp=c(north,south), 
    region=c(rep("north",length=3060),rep("south",length=3060)))

#manipulating into cdf, as I've seen in other examples
temp.regions <- ddply(df_temp, .(region), summarize,
                          temp = unique(temp),
                          ecdf = ecdf(temp)(unique(temp)))

# feeding into ggplot. 
 ggplot(temp.regions,aes(x=temp, y=ecdf, color = region)) + 
      geom_line(aes(x=temp,color=region))+
      scale_colour_manual(values = c("blue","red"))

What I would then like, would be to shade both curves for temperatures below 0.2 on the y axis. Ideally I'd like to see the blue one shaded in blue, and the red one shaded in red. Then, where they cross over in purple.

However, the closest I have managed is as follows... ]

Which I have achieved using the following additions to my code.

# creating a dataframe with just the temperatures for below 0.2
# to try and aid control when plotting
temp.below <- temp.regions[which(temp.regions$ecdf<0.2),]

# plotting routine again. 
ggplot(temp.regions, aes(x=temp, y=ecdf, color = region)) + 
  geom_line(aes(x=temp,color=region))+
  scale_colour_manual(values = c("blue","red"))+
# with additional line for shading.
  geom_ribbon(data=temp.below,
              aes(x=temp,ymin=0,ymax=0.2), alpha=0.5)

I've seen a few examples of people shading for a normal distribution density plot, which is where I have adapted my code from. But for some reason my boxes don't seem to want anything to do with the temperature curve.

Please help! I'm sure it's quite simple, I'm just really lost and have tried a few, producing less convincing results than these.

Thank you so much for taking a look.

PROBLEM SOLVED THANKS TO HELP BELOW...

running suggested code from below

geom_ribbon(aes(ymin=0,ymax=ecdf, fill=region), alpha=0.5)

gives...

which is so very almost the solution I'm after, but with one final addition... like so

#geom_ribbon(aes(ymin=0,ymax=ecdf, fill=region), alpha=0.5)
geom_ribbon(data=temp.below, aes(ymin=0,ymax=ecdf, fill=region), alpha=0.5)

I get what I'm after...

The reason I set the data again is so that it only fills the lowest 20% of the two regions.

Thank you so much for the help :-)

Answer 1

Looks like you're thinking about it in the right way. With geom_ribbon i dont think you need to set data to anything else. Just set aes(ymin = 0, ymax = ecdf, fill = region). I think that should do it.