How to use geom_errorbar to indicate standard error in ggplot2-CodePudding

Lets say I have a data table called dt

| group | value |
| -     | -     |
| a     | 1     |
| b     | 2     |
| a     | 3     |
| b     | 4     |
| a     | 5     |

And I already have my Jittered Strip Plot and I need to indicate the standard error in ggplot2 by using geom_error. Since there are two varibles a and b in column group. How do I specify the group when I calculate mean() and sd() in the geom_error function

Do I have to create another table to store mean and sd for my dataset?

CodePudding user response：

The way to do it is to compute the summary statistics before the plot.

suppressPackageStartupMessages({
  library(ggplot2)
  library(data.table)
})

setDT(dt)
dt[, c("mean", "sd") := list(mean(value), sd(value)), by = group]

ggplot(dt, aes(group, value))  
  geom_jitter()  
  geom_errorbar(aes(ymin = mean - sd, ymax = mean   sd), width = 0.5)

^{Created on 2022-10-05 with}

Data used

set.seed(2)

dt <- data.frame(group = sample(c("a", "b"), 20, TRUE),
                 value = sample(100, 20, TRUE))