quote()/eval() question

Dear list,

For a reason it would take me long to explain, I need to do something along
the lines of what's shown below -- i.e., create an object from
dplyr::summarise, and then evaluate it on a data frame.

I know I could directly do:

  df %>% dplyr::summarise(x1_mean = mean(x1))

but this is not what I'm looking for.


library(dplyr)

df <- data.frame(x1 = rnorm(100), x2 = rnorm(100))

foo <- function(df) {

   mySummary <- quote(dplyr::summarise(x1_mean = mean(x1)))

   df %>% eval(mySummary)

}

foo(df)

Error in eval(., mySummary) : invalid 'envir' argument of type 'language'

Thank you,
Axel.

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