问题
Somewhat hard to define this question without sounding like lots of similar questions!
I have a function for which I want one of the parameters to be a function name, that will be passed to dplyr::summarise, e.g. "mean" or "sum":
data(mtcars)
f <- function(x = mtcars,
groupcol = "cyl",
zCol = "disp",
zFun = "mean") {
zColquo = quo_name(zCol)
cellSummaries <- x %>%
group_by(gear, !!sym(groupcol)) %>% # 1 preset grouper, 1 user-defined
summarise(Count = n(), # 1 preset summary, 1 user defined
!!zColquo := mean(!!sym(zColquo))) # mean should be zFun, user-defined
ungroup
}
(this groups by gear and cyl, then returns, per group, count and mean(disp))
Per my note, I'd like 'mean' to be dynamic, performing the function defined by zFun, but I can't for the life of me work out how to do it! Thanks in advance for any advice.
回答1:
You can use match.fun to make the function dynamic. I also removed zColquo as it's not needed.
library(dplyr)
library(rlang)
f <- function(x = mtcars,
groupcol = "cyl",
zCol = "disp",
zFun = "mean") {
cellSummaries <- x %>%
group_by(gear, !!sym(groupcol)) %>%
summarise(Count = n(),
!!zCol := match.fun(zFun)(!!sym(zCol))) %>%
ungroup
return(cellSummaries)
}
You can then check output
f()
# A tibble: 8 x 4
# gear cyl Count disp
# <dbl> <dbl> <int> <dbl>
#1 3 4 1 120.
#2 3 6 2 242.
#3 3 8 12 358.
#4 4 4 8 103.
#5 4 6 4 164.
#6 5 4 2 108.
#7 5 6 1 145
#8 5 8 2 326
f(zFun = "sum")
# A tibble: 8 x 4
# gear cyl Count disp
# <dbl> <dbl> <int> <dbl>
#1 3 4 1 120.
#2 3 6 2 483
#3 3 8 12 4291.
#4 4 4 8 821
#5 4 6 4 655.
#6 5 4 2 215.
#7 5 6 1 145
#8 5 8 2 652
回答2:
We can use get
library(dplyr)
f <- function(x = mtcars,
groupcol = "cyl",
zCol = "disp",
zFun = "mean") {
zColquo = quo_name(zCol)
x %>%
group_by(gear, !!sym(groupcol)) %>% # 1 preset grouper, 1 user-defined
summarise(Count = n(), # 1 preset summary, 1 user defined
!!zColquo := get(zFun)(!!sym(zCol))) %>%
ungroup
}
f()
# A tibble: 8 x 4
# gear cyl Count disp
# <dbl> <dbl> <int> <dbl>
#1 3 4 1 120.
#2 3 6 2 242.
#3 3 8 12 358.
#4 4 4 8 103.
#5 4 6 4 164.
#6 5 4 2 108.
#7 5 6 1 145
#8 5 8 2 326
f(zFun = "sum")
# A tibble: 8 x 4
# gear cyl Count disp
# <dbl> <dbl> <int> <dbl>
#1 3 4 1 120.
#2 3 6 2 483
#3 3 8 12 4291.
#4 4 4 8 821
#5 4 6 4 655.
#6 5 4 2 215.
#7 5 6 1 145
#8 5 8 2 652
In addition, we could remove the sym evaluation in group_by and in summarise if we wrap with across
f <- function(x = mtcars,
groupcol = "cyl",
zCol = "disp",
zFun = "mean") {
x %>%
group_by(across(c(gear, groupcol))) %>% # 1 preset grouper, 1 user-defined
summarise(Count = n(), # 1 preset summary, 1 user defined
across(zCol, ~ get(zFun)(.))) %>%
ungroup
}
f()
# A tibble: 8 x 4
# gear cyl Count disp
# <dbl> <dbl> <int> <dbl>
#1 3 4 1 120.
#2 3 6 2 242.
#3 3 8 12 358.
#4 4 4 8 103.
#5 4 6 4 164.
#6 5 4 2 108.
#7 5 6 1 145
#8 5 8 2 326
来源：https://stackoverflow.com/questions/62906259/r-user-defined-dynamic-summary-function-within-dplyrsummarise