ggplot轴：图的左侧和右侧不同的y轴

Question

I have the following data;

https://www.dropbox.com/s/at2f2zni7s1hnzm/results.csv?dl=0

When I plot all three plots using the following;

library(ggplot2)
library(pROC)
    roc <- roc(results$testactual, results$pred)
    ggroc(roc) +
      geom_density(data = results %>%
                     filter(testactual == 0), aes(pred), color='green') + 
      geom_density(data = results %>%
                     filter(testactual == 1), aes(pred), color='black')

I am able to obtain 3 plots on the same graph but the axis are not as I would have hoped.

I am trying to make it such that the y-axis for the density plots are displayed onto the right side and the roc plots y-axis are on the left.

Finally sort the x-axis so that the 1 is on the right side and the zero is on the left side (however I think I can manage this as I have run into this problem before)

Direct R link to data:

results <- read.csv(url("https://www.dropbox.com/s/at2f2zni7s1hnzm/results.csv?dl=1"))

EDIT: Just plotting the density plots:

Plot of the ROC plot

Answer 1

Use the sec.axis parameter. Also you can use ..scaled.. to scale your densities to max of 1.

roc <- roc(results$testactual, results$pred)
ggroc(roc) +
  geom_density(data = results %>%
                 filter(testactual == 0), aes(x=pred, y=..scaled..), color='green') + 
  geom_density(data = results %>%
                 filter(testactual == 1), aes(x=pred, y=..scaled..), color='black') +
scale_y_continuous(name = "Density", sec.axis = sec_axis(~., name = "Sensitivity"))