Calculations based on Quartiles (Any percentile)-CodePudding

For example

summary(mtcars$mpg)
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
  10.40   15.43   19.20   20.09   22.80   33.90

I need to calculate of mean and standard deviation of "disp" variable of each quartile based on variable "mpg".

CodePudding user response：

Specify the breaks with the quantile of 'mpg' in cut, use that as grouping variable to summarise the mean and sd of 'disp'

library(dplyr)
mtcars %>%
     group_by(mpg_grp = cut(mpg, breaks = c(-Inf, quantile(mpg), Inf))) %>% 
     summarise(disp_mean = mean(disp), disp_sd = sd(disp))