ggroc with several line colors

[ProfBiscuit]

Hello,

I am using your amazing package to plot multiple ROC curves on the same axis. What I am attempting to do is plot, say, 5 ROC curves that are one color and a sixth ROC curve that is red.

I understand that this topic has been raised before ( #issue #42 ) however, I do not understand how the code modification you pushed addressed this request.

For example, if I was plotting 5 curves, would it be doable for 'color' to be fed a list of length 5 such as 'colour = c(rep('grey', 4), 'red')?

My exact scenario is similar to this, although in my real-world situation the models are far more informative (I hope).

library(pROC)
library(dplyr)
library(purrr)

df <- data.frame(
  truth = rbinom(n = 1000, size = 1, prob = 0.5),
  pred.prob = runif(n = 1000),
  group = factor(rep(LETTERS[1:5], times = 200))
)

df.list <- df %>% 
  group_split(group)

map_function <- function(x){
  pROC::roc(
    data = x,
    response = truth,
    predictor = pred.prob
  )
}

roc.list <- map(df.list, map_function)

ggroc(roc.list, color = "grey", alpha = 0.5) +
  ggplot2::theme_bw()

Given how your package is currently written, how could this be accomplished?

Thanks!

[xrobin]

Quick answer, don't have time to look at it in much detail now.
Issue #42 is implicitly about using automatic mapping of several aesthetics, which is irrelevant to you.
So you should leave it empty or maybe set it to "group" (I can't remember what's the default right now) and define a vector of colors as you proposed. I believe these should be passed to geom_line, although I can't remember testing it.

[ProfBiscuit]

Ah, sure. scale_color_manual seems to do the job.

library(pROC)
library(dplyr)
library(purrr)
library(ggplot2)

df <- data.frame(
  truth = rbinom(n = 1000, size = 1, prob = 0.5),
  pred.prob = runif(n = 1000),
  group = factor(rep(LETTERS[1:5], times = 200))
)

df.list <- df %>% 
  group_split(group)

map_function <- function(x){
  pROC::roc(
    data = x,
    response = truth,
    predictor = pred.prob
  )
}

roc.list <- map(df.list, map_function)

ggroc(roc.list, alpha = 0.5) +
  scale_color_manual(values=c(rep('grey', 4), 'red')) + 
  theme_bw()

Thank you!

[xrobin]

Oh that shouldn't be necessary. I don't remember having to use that with geom_line...
Or if it is it should be at least documented / mentioned. I'm reopening the issue and will look into it soon.

[xrobin]

Of course one can't pass a vector of colors to geom_lines, I'm not sure why I thought it would be doable.
Indeed you need to use one of the scale_color_* function as you would to change colors in general with ggplot2. And make sure you map the aesthetic, so aes="color" is needed.
I've updated the documentation with an example. It always takes me too much time to figure out how to customize a ggplot2 plot so an example can't hurt.
Thanks for bringing this issue to my knowledge!