如何按组计算平均值和标准差，并将格式设置为 dataframe？

Question

My data is currently in the format of df1:

outcome <- c("success", "failure", "success", "failure", "success", "failure")
basketball <- c(10, 7, 7, 8, 9, 10)
soccer <- c(8, 21, 30,  21, 6, 10)
football <- c(9,  2,  1, 3, 1, 5)

df1 <-  data.frame(outcome, basketball, soccer, football)

And I would like it to be in the format of df2, so I can more easily create a bar graph with ggplot2.

symptom <-  c("basketball",  "basketball", "soccer", "soccer", "football", "football")
mean <-  c(10, 6, 9, 7, 3, 1)
sd <-  c(1, 2, 1, 3, 0.5, 0.2)

df2 <- data.frame(outcome, symptom, mean, sd)

Currently I have a lot of code that can get me there in a roundabout way, but I feel like there must be a streamlined way to do this in a few lines of code. Is there a way to use this using dplyr or tidyr verbs?

Thanks!

Answer 1

We can reshape to 'long' format with pivot_longer and then do a group by operation

library(dplyr)
library(tidyr)
df1 %>%
  pivot_longer(cols = basketball:football, names_to = 'symptom') %>% 
  group_by(outcome, symptom) %>%
  summarise(mean = mean(value), sd = sd(value), .groups = 'drop')

If we also need to plot

library(ggplot2)
df1 %>%
  pivot_longer(cols = basketball:football, names_to = 'symptom') %>% 
  group_by(outcome, symptom) %>% 
  summarise(mean = mean(value), sd = sd(value), .groups = 'drop') %>%
  ggplot(aes(x = outcome, y = mean, fill = symptom)) + 
    geom_bar(position = position_dodge(), stat = 'identity') + 
    geom_errorbar(aes(ymin = mean - sd, ymax = mean + sd),
            width = .2, position = position_dodge(.9))