rfilterdplyr

r dplyr filter with a dynamic variable name

I am trying to select only the rows without NAs:

library(dplyr)
x = data.frame(a = c(NA, 2, 3, 4))
var_a <- "a"
# This works:
x %>% filter(!is.na(a))
# That works too:
var_a <- quo(a)
x %>% filter(!is.na(!!var_a))
# But this doesn't work:
var_a <- "a"
x %>% filter(!is.na(!!var_a))

What should I change in the last line for it to work? Because I have to work with var_a <- "a". Thank you very much!

Solution

  • It is a string, so we can convert to symbol with sym and then use !!

    x %>% 
   filter(!is.na(!!rlang::sym(var_a)))
#  a
#1 2
#2 3
#3 4

    Or another option is to specify the object in filter_at and then do the filtering

    x %>% 
   filter_at(var_a, all_vars(!is.na(.)))
#  a
#1 2
#2 3
#3 4