CODEWITHSUNDEEP
rdplyr
The Bolt
The Bolt

Reputation: 121

Standard Evaluation to calculate the mean using summarise()

So I am taking a column name which is guaranteed to exist in the data frame as the input, and want to calculate the mean of the given column (Let's suppose c is the parameter in the function).

EDIT: Tried recreating a scenario here.

states <- c("Washington", "Washington", "California", "California")
random.data <- c(10, 20, 30, 40)
data <- data.frame(states, random.data)

data.frame <- data %>%
              group_by(states) %>%
              summarise_(average = mean(paste0("random", ".data")))

When I tried doing this I got the following error:

Warning message:
In mean.default(paste0("random", ".data")) :
    argument is not numeric or logical: returning NA

I have an idea about standard evaluation, but for some reason it is not working for this mean function.

Upvotes: 1

Views: 39

Answers (1)

akrun
akrun

Reputation: 887911

We can use sym with !!

col <- paste0("random", ".data")
data %>%
   group_by(states) %>% 
   summarise(average = mean(!! rlang::sym(col)))
   ##or use directly
   #summarise(average = mean(!! rlang::sym(paste0("random", ".data"))))

# A tibble: 2 x 2
#      states average
#     <fctr>   <dbl>
#1 California      35
#2 Washington      15

Or another option is get

data %>%
    group_by(states) %>% 
    summarise(average = mean(get(paste0("random", ".data"))))
# A tibble: 2 x 2
#     states average
#      <fctr>   <dbl>
#1 California      35
#2 Washington      15

Upvotes: 1

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