wrong color in geom_ribbon?

Question

Consider this simple example

library(dplyr)
library(ggplot2)
library(lubridate)

testdf <- data_frame(time = c(ymd('2015-01-01'), ymd('2015-02-01'), ymd('2015-03-01')),
                     coef = c(1, 0, -1),
                     low_ci = c(-0.5, -0.25, -2),
                     high_ci = c(1.5, 0.5, -.5))

> testdf
# A tibble: 3 x 4
  time        coef low_ci high_ci
  <date>     <dbl>  <dbl>   <dbl>
1 2015-01-01     1  -0.5      1.5
2 2015-02-01     0  -0.25     0.5
3 2015-03-01    -1  -2       -0.5

Here I want to plot the time series of coef, using the low_ci and high_ci as confidence interval bands.

However, using the following code produces a surprising result

testdf %>% 
  ggplot(., aes(x = time)) + 
  geom_line(aes(y = coef)) +
  geom_ribbon(aes(ymin = low_ci, ymax = high_ci , alpha = 0.3, fill = 'blue'))

Since when blue is red?! What is the issue here?

Thanks!!

"Blue" is treated as a grouping value and gets a colour automatically, which happens to be the one you see. Whatever you type in `fill=` you'll get the same colour :) — AntoniosK, Aug 09 '18 at 12:58
thanks, but what if I had another `fill` for the first `geom_`, say `geom_point()`. wouldnt they be confused? — ℕʘʘḆḽḘ, Aug 09 '18 at 13:02
thanks! perhaps you can post this as a solution? can you also fix the bogus legend here? does not make any sense at the moment lol! thanks!! — ℕʘʘḆḽḘ, Aug 09 '18 at 13:05

demarsylvain · Accepted Answer · 2018-08-09T13:35:32.210

2

As AntoniosK said, you can use the function scale_fill_manual(), but a second option is to put the parameter fill = 'blue' outside of the function aes() (same thing for the parameter alpha). Like this :

testdf %>% 
  ggplot(., aes(x = time)) + 
  geom_line(aes(y = coef)) +
  geom_ribbon(aes(ymin = low_ci, ymax = high_ci), alpha = 0.3, fill = 'blue')

edited Aug 09 '18 at 13:35

answered Aug 09 '18 at 13:33

demarsylvain

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thanks! but how to fix the wrong label then? Alpha does not mean anything here – ℕʘʘḆḽḘ Aug 09 '18 at 13:34
put `alpha = 0.3` outside of `aes()`. I edited the solution. – demarsylvain Aug 09 '18 at 13:36
@demarsylvain thanks! last tweak, how can I now add a label that say coef is the black line? and the ribbon are confidence intervals? – ℕʘʘḆḽḘ Aug 09 '18 at 13:46

wrong color in geom_ribbon?

1 Answers1