sym not working with vector has more than 1 element-CodePudding

df <- data.frame(A = c(1,1,1), B = c(2,2,3))
variables <- c("A", "B") 
dplyr::count(df, !!!rlang::sym(variables))

Error: Only strings can be converted to symbols
Run `rlang::last_error()` to see where the error occurred.

It works if variables is either A or B, but not both.

CodePudding user response：

For this syms is needed. According to ?sym

sym() creates a symbol from a string and syms() creates a list of symbols from a character vector.

dplyr::count(df, !!!rlang::syms(variables))
  A B n
1 1 2 2
2 1 3 1

CodePudding user response：

There are several ways to do this. The problem with the OPs method is that sym() will return a single symbol, but we need a list of symbols. Use the excellent answer by akrun, with the vectorized syms or purrr::map(sym).

Or, without rlang, double/tripple bangs etc, we can do it within dplyr with across(all_of())

Library(tidyverse)

count(df, !!!syms(variables)) #As suggested by @akrun

count(df, across(all_of(variables)))

count(df, !!!map(variables, sym))

  A B n
1 1 2 2
2 1 3 1