passing column reference to group_by in an R function

Question

This question is related to the a similar post. Function writing passing column reference to group_by

However, I want to pass several inputs to a function that uses group_by_() and summarise_().

Here's my function:

foo <- function(data,column,x1,x2){
    data %>%
            group_by_(.dots = column) %>%
            summarise_(.dots= c(~mean(x1), ~mean(x2)))
}

However, when I run

foo(mtcars,"cyl", "disp", "hp")

I get the following error.

Error in UseMethod("as.lazy_dots") : 
  no applicable method for 'as.lazy_dots' applied to an object of class "c('double', 'numeric')"
In addition: Warning message:
In mean.default(x1) : argument is not numeric or logical: returning NA

Can anyone tell me where I'm doing wrong?

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score 6 · Accepted Answer · answered Oct 22 '15 at 21:27

Well, it looks like you just want summarise_each again, which does have a standard evaulation alternative, summarise_each_. You can write foo as

foo <- function(data, column, x1, x2){
    data %>%
            group_by_(.dots = column) %>%
            summarise_each_(funs(mean), c(x1,x2))
}

and call it with

foo(mtcars,"cyl", "disp", "hp")
# Source: local data frame [3 x 3]
# 
#     cyl     disp        hp
#   (dbl)    (dbl)     (dbl)
# 1     4 105.1364  82.63636
# 2     6 183.3143 122.28571
# 3     8 353.1000 209.21429

Oh, thank you so much David! I didn't know I could pass specific variables to summarise_each_ :) — asiehh, Oct 22 '15 at 21:31

passing column reference to group_by in an R function

1 Answers1