When using dplyr:filter, I often compute a local variable that holds the viable choices:
df <- as_tibble(data.frame(id=c("a","b"), val=1:6))
ids <- c("b","c")
filter(df, id %in% ids)
# giving id %in% c("b","c")
However, if the dataset by chance has a column with the same name, this fails to achieve the intended purpose:
df$ids <- "a"
filter(df, id %in% ids)
# giving id %in% "a"
How should I explicitly refer to the ids variable instead of the ids column?
Unquote with !! to tell filter to look in the calling environment instead of the data frame:
library(tidyverse)
df <- data_frame(id = rep(c("a","b"), 3), val = 1:6)
ids <- c("b", "c")
df %>% filter(id %in% ids)
#> # A tibble: 3 x 2
#> id val
#> <chr> <int>
#> 1 b 2
#> 2 b 4
#> 3 b 6
df <- df %>% mutate(ids = "a")
df %>% filter(id %in% ids)
#> # A tibble: 3 x 3
#> id val ids
#> <chr> <int> <chr>
#> 1 a 1 a
#> 2 a 3 a
#> 3 a 5 a
df %>% filter(id %in% !!ids)
#> # A tibble: 3 x 3
#> id val ids
#> <chr> <int> <chr>
#> 1 b 2 a
#> 2 b 4 a
#> 3 b 6 a
Of course, the better way to avoid such issues is to not put identically-named vectors in your global environment.
