stat_summary() 和 fun.data = mean_sdl 不起作用

Question

set.seed(1) # generate random data
day1 = rnorm(20,0,1)
day2 = rnorm(20,5,1)
Subject <- rep(paste0('S',seq(1:20)), 2)
Data <- data.frame(Value = matrix(c(day1,day2),ncol=1))
Day <- rep(c('Day 1', 'Day 2'), each = length(day1))
df <- cbind(Subject, Data, Day)

Using this random data, I'd like to plot individual points with unique color for each subject and a summary point (mean + standard deviation).

It seems that the plot is okay when all points are plotted with the same color because stat_summary(fun.data = mean_sdl) works properly.

ggplot(data = df, mapping = aes(x= Day, y =Value)) +
  stat_summary(fun.data = mean_sdl, fun.args = list(mult = 2),
               geom = 'pointrange', fatten = 3*1.2, size = 1.2,
               color= 'black')  +
  geom_point(size = 2) 

But not when all points have unique color (for each subject).

ggplot(data = df, mapping = aes(x = Day, y = Value,
                                fill = Subject)) +
  stat_summary(fun.data = mean_sdl, fun.args = list(mult = 2),
               geom = 'pointrange', fatten = 3*1.2, size = 1.2,
               color = 'black') +
  geom_point(shape = 21, color = 'white', size = 2) 

Answer 1

In your example ggplot assumes that each color corresponds to an individual group, but you want the grouping and color to be separate. Therefore, you need to explicitly define the group to be "Day".

ggplot(data = df, mapping = aes(x = Day, y = Value,
                                fill = Subject, group = Day)) +
  stat_summary(fun.data = mean_sdl, fun.args = list(mult = 2),
               geom = 'pointrange', fatten = 3*1.2, size = 1.2,
               color = 'black') +
  geom_point(shape = 21, color = 'white', size = 2) 

Answer 2

Try the following:

ggplot(data = df, mapping = aes(x= Day, y =Value)) +
  stat_summary(fun.data = mean_sdl, fun.args = list(mult = 2),
               geom = 'pointrange', fatten = 3*1.2, size = 1.2,
               color= 'black')  +
  geom_point(size = 2, aes(color = Subject)) 

Instead of specifying fill in aes() in the first line ( ggplot(...) ), I've moved it to the geom_point() element instead. Otherwise, stat_summary() will be doing its calculations grouped using Subject !