On 08/09/2017 7:55 PM, Axel Urbiz wrote:
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)
magrittr pipes are just syntactic sugar. What your second line does is
the same as
eval(df, mySummary)
which makes no sense. These would work:
eval(df, expr = mySummary)
eval(mySummary, envir = df)
You could write the first as
df %>% eval(expr = mySummary)
and the second as
df %>% eval(mySummary, envir = .)
Duncan Murdoch
}
foo(df)
Error in eval(., mySummary) : invalid 'envir' argument of type 'language'
Thank you,
Axel.
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