Can not use dynamic variable names with dplyr in r

问题

I see the answers on this website, but it can not solve my problem.

What I want is that use dynamic variable names both on LHS and RHS within summarize.

This is a simple example to show what I have tried:

why I use paste0('carb') not use carb directly is that on the position(paste0('carb')) is a dynamic variable like this paste0('temp', n) and n is a series of numbers in my real situation.

library(dplyr)
sumay1 <- mtcars %>% group_by(cyl) %>% 
  summarise(!!paste0('carb', 100) := mean(paste0('carb'), na.rm = T))

sumay2 <- mtcars %>% group_by(cyl) %>% 
  summarise(!!paste0('carb', 100) := mean(sym('carb'), na.rm = T))

sumay3 <- mtcars %>% group_by(cyl) %>% 
  summarise(!!paste0('carb', 100) := mean({{paste0('carb')}}, na.rm = T))

回答1:

In the second case, we need to evaluate (!!) the symbol

library(dplyr)
mtcars %>% 
   group_by(cyl) %>% 
   summarise(!!paste0('carb', 100) := mean(!!sym('carb'), na.rm = TRUE))
# A tibble: 3 x 2
#    cyl carb100
#* <dbl>   <dbl>
#1     4    1.55
#2     6    3.43
#3     8    3.5 

The {{}} is mainly used within a function where we pass unquoted arguments and it is equivalent to enquo + !!

来源：https://stackoverflow.com/questions/61976957/can-not-use-dynamic-variable-names-with-dplyr-in-r