Using summarize_all with colMeans and colVar to create pivoted table in R

Question

I want to use summarize_all on the following data and create my desired output, but I was curious how to do this the tidy way using some combination of mutate and summarize I think? Any help appreciated!!

dummy <- tibble(
  a = 1:10,
  b = 100:109,
  c = 1000:1009
)

Desired Output

tibble(
  Mean = colMeans(dummy[1:3]),
  Variance = colVars(as.matrix(dummy[1:3])),
  CV = Variance/Mean
)

    Mean Variance      CV
   <dbl>    <dbl>   <dbl>
1    5.5     9.17 1.67   
2  104.      9.17 0.0877 
3 1004.      9.17 0.00913

Answer 1

It would be easier to reshape to 'long' format and then do it once after grouping by 'name'

library(dplyr)
library(tidyr)
pivot_longer(dummy, cols = everything()) %>% 
  group_by(name) %>% 
  summarise(Mean = mean(value), Variance = var(value), CV = Variance/Mean) %>%
  select(-name)
# A tibble: 3 x 3
#    Mean Variance      CV
#   <dbl>    <dbl>   <dbl>
#1    5.5     9.17 1.67   
#2  104.      9.17 0.0877 
#3 1004.      9.17 0.00913

---

Or either use summarise_all or summarise/across, but the output would be a single row, then do the reshaping

dummy %>% 
   summarise(across(everything(), list(Mean = mean,
         Variance = var, CV = ~ mean(.)/var(.)))) %>%
   pivot_longer(everything()) %>% 
   separate(name, into = c('name', 'name2')) %>% 
   pivot_wider(names_from = name2, values_from = value)