Why doesn't dplyr filter() work within function (i.e. using variable for column name)?

Question

A function for filtering, grouping and mutating data with dplyr functions. Basic pipe sequence works great outside a function, that is where I use the true column names. Put it in a function where the column name is a variable and some of the functions work but some don't most notably dplyr::filter(). For example:

var1 <- c('yes', NA, NA, 'yes', 'yes', NA, NA, NA, 'yes', NA, 'no', 'no', 'no', 'maybe', NA, 'maybe', 'maybe', 'maybe')

var2 <- c(1:18)

df <- data.frame(var1, var2)

This works fine (i.e. filters NA's):

df%>%filter(!is.na(var1))

...but this doesn't:

x <- "var1"

df%>%filter(!is.na(x))

...but this does:

df%>%select(x)

It's NA's that need to be filtered out specifically.

Tried get("x"), no good, and slicing:

df[!is.na(x),]

...no good, either.

Any ideas on how to pass a variable to filter inside (or outside) a function and why a variable is working with other dplyr functions?

Answer 1

We can use the sym to convert to a symbol and then with UQ evaluate it

library(rlang)
library(dplyr)
df %>%
   filter(!is.na(UQ(sym(x))))
#     var1 var2
#1    yes    1
#2    yes    4
#3    yes    5
#4    yes    9
#5     no   11
#6     no   12
#7     no   13
#8  maybe   14
#9  maybe   16
#10 maybe   17
#11 maybe   18