CODEWITHSUNDEEP
rdplyr
Eric
Eric

Reputation: 1389

passing variable to dplyr as string

I must be missing something reading the tidyverse programming vignette. For this example:

library(dplyr)
library(entropy)

set.seed(122)
df <-data.frame(vec = sample(letters[1:20],100,replace = T),val = sample(1:10,100,replace = T))

df %>%
  group_by(vec) %>%
  filter(
    n()>4,
    entropy(table(val))>0
  )
# A tibble: 62 x 2
# Groups:   vec [8]
   vec     val
   <fct> <int>
 1 s        10
 2 s         8
 3 d         4
 4 a         2
 5 l         4
 6 m         4
 7 a         5
 8 a         9
 9 l         4
10 s         6
# ... with 52 more rows

I would like to pass the value variable as a string but this doesn't work here:

var_name="val"

df %>%
  group_by(vec) %>%
  filter(
    n()>4,
    entropy(table(!! var_name))>0
  )
# A tibble: 0 x 2
# Groups:   vec [1]
# ... with 2 variables: vec <fct>, val <int>

What am I missing?

Upvotes: 0

Views: 58

Answers (1)

G. Grothendieck
G. Grothendieck

Reputation: 269491

Use !!sym(var_name) like this:

df %>%
  group_by(vec) %>%
  filter(
    n()>4,
    entropy(table(!!sym(var_name)))>0
  )

Upvotes: 1

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