Find points over and under the confidence interval when using geom_stat / geom_smooth in ggplot2

Question

I have a scatter plot,I want to know how can I find the genes above and below the confidence interval lines?

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EDIT: Reproducible examp

Answer 1

This solution takes advantage of the hard work ggplot2 does for you:

library(sp)

# we have to build the plot first so ggplot can do the calculations
ggplot(df,aes(mpg,cyl)) +
  geom_point() +
  geom_smooth() -> gg

# do the calculations
gb <- ggplot_build(gg)

# get the CI data
p <- gb$data[[2]]

# make a polygon out of it
poly <- data.frame(
  x=c(p$x[1],    p$x,    p$x[length(p$x)],    rev(p$x)), 
  y=c(p$ymax[1], p$ymin, p$ymax[length(p$x)], rev(p$ymax))
)

# test for original values in said polygon and add that to orig data
# so we can color by it
df$in_ci <- point.in.polygon(df$mpg, df$cyl, poly$x, poly$y)

# re-do the plot with the new data
ggplot(df,aes(mpg,cyl)) +
  geom_point(aes(color=factor(in_ci))) +
  geom_smooth()

It needs a bit of tweaking (i.e that last point getting a 2 value) but I'm limited on time. NOTE that the point.in.polygon return values are:

• 0: point is strictly exterior to pol
• 1: point is strictly interior to pol
• 2: point lies on the relative interior of an edge of pol
• 3: point is a vertex of pol

so it should be easy to just change the code to TRUE/FALSE whether value is 0 or not.