Two geom_ribbon

I want some figure like this two geom_riboon from: https://doi.org/10.1016/j.neuroimage.2019.116060

This is head of my data:

  time        mean         sem class
1 -200 -0.03459213 0.002035373     n
2 -196 -0.03065102 0.001801943     n
3 -192 -0.02696143 0.001602451     n
4 -188 -0.02354627 0.001436726     n
5 -184 -0.02040872 0.001302610     n
6 -180 -0.01753815 0.001196551     n

I wrote this code:

    ggplot(df, aes(time,
           color = class)) + 
  geom_line(mapping = aes(y = mean))
  geom_ribbon(aes(y = mean,
                  ymin = mean - sem,
                  ymax = mean + sem,
                  color = class))

But it doesn't create shaded area and I only see the mean line.

Your problem is that geom_line and geom_ribbon require different aesthetics: for geom_line you need to set color, for geom_ribbon one uses fill:

library(tidyverse)

df <- expand.grid(time = 1:100, class = c("n", "m"))
df$mean <- cumsum(rnorm(200)) / 2
df$sem <- runif(200) / 2 + .1

head(df)
#>   time class       mean       sem
#> 1    1     n -0.4234046 0.2881793
#> 2    2     n -0.7435868 0.1144850
#> 3    3     n  0.4751080 0.5943168
#> 4    4     n -0.3778799 0.1435532
#> 5    5     n -0.7692029 0.1378587
#> 6    6     n -0.9309995 0.1538270

ggplot(df, aes(time)) +
  geom_line(aes(y = mean, color = class)) +
  geom_ribbon(aes(ymin = mean - sem, ymax = mean + sem, fill = class), alpha = .5)

^{Created on 2022-07-05 by the reprex package (v2.0.1)}