passing function argument to dplyr select

Question

I can do this to pick out a few columns from a dataframe.

require(dplyr)

require(magrittr)

df - data.frame (col1 = c(1, 2, 3), col2 = letters[1:3], col3 = LETTERS[4:6])

percent > df percent

select (col1, col2)

I'd like to create a function that works like

F is a function (data, firstCol, secondCol)

{

information percent > percent

substitute (firstCol, secondCol) in the choose box

}

But when I run f(df, col1, col2), I get an error.

Select vars(names(.data),..., env = parent.frame()) has encountered an error:

It is impossible to force a (list) object to type "double."

originating from: (function ()

{

.rs.breakOnError(TRUE)

})()

EDIT -- slightly less trivial example:

Suppose I wanted to do

mtcars %>%

select(cyl, hp) %>%

unique %>%

group_by(cyl) %>%

summarise(avgHP = mean(hp))

but with different datasets and different variable names. I could reuse the code and replace mtcars, cyl, and hp. But I'd rather wrap it all up in a function