使用plyr和泛型函数对数据框的每一列进行操作，同时保留名称(Using plyr and generic functions to operate on each column of a data frame while preserving names)

我试图使用通用函数来操作数据框中的每一列，其中操作将根据列的类别而变化。

我无法让函数访问列的名称，同时还将列调度到正确的方法。

df <- data.frame(f1 = factor(rep(1:3, 2))) myfun <- function(x){ UseMethod("myfun", x) } myfun.factor <- function(x){ print("Using factor method") print(names(x)) print(class(x)) } myfun.default <- function(x){ print("Using default method") print(names(x)) print(class(x)) }

作为列表应用可以提供正确的调度，但可以从列中删除名称

library(plyr) l_ply(df, myfun) [1] "Using factor method" NULL [1] "factor"

作为数组应用会保留名称，但不会提供正确的名称

a_ply(df, 2, myfun) [1] "Using default method" [1] "f1" [1] "data.frame"

有没有一种方法可以充分利用这两种方法，还是坚持使用本问题答案中描述的方法？

I'm trying to use a generic function to operate on each column of a data frame where the operation will vary depending on the class of the column.

I'm having trouble giving the function access to the names of the columns while also dispatching the columns to the correct method.

df <- data.frame(f1 = factor(rep(1:3, 2))) myfun <- function(x){ UseMethod("myfun", x) } myfun.factor <- function(x){ print("Using factor method") print(names(x)) print(class(x)) } myfun.default <- function(x){ print("Using default method") print(names(x)) print(class(x)) }

Applying as a list gives the correct dispatch but strips the names from the columns

library(plyr) l_ply(df, myfun) [1] "Using factor method" NULL [1] "factor"

Applying as an array retains the names but doesn't give the correct names

a_ply(df, 2, myfun) [1] "Using default method" [1] "f1" [1] "data.frame"

Is there a neat way to get the best of both or am I stuck with the method described in the answer to this question?

最满意答案

我无法找到这个问题的直接解决方案，但我确实找到了一个我非常满意的工作。 我使用了一个中间函数，该函数接受由a*ply传递给它的列并传递一个未unlist表单，并将其名称传递给泛型函数。

myfun2 <- function(x, x_name){ UseMethod("myfun2", x) } myfun2.factor <- function(x, x_name){ print("Using factor method") print(x_name) print(class(x)) return(NULL) } myfun2.default <- function(x, x_name){ print("Using default method") print(x_name) print(class(x)) return(NULL) } dispatch_fun <- function(x){ myfun2(unlist(x), names(x)) } a_ply(df, 2, dispatch_fun) ## [1] "Using factor method" ## [1] "f1" ## [1] "factor"

I wasn't able to find a direct solution to this question, however I did find a work around I'm fairly happy with. I used an intermediary function which takes the column passed to it by a*ply and passes an unlisted form and it's name to the generic function.

myfun2 <- function(x, x_name){ UseMethod("myfun2", x) } myfun2.factor <- function(x, x_name){ print("Using factor method") print(x_name) print(class(x)) return(NULL) } myfun2.default <- function(x, x_name){ print("Using default method") print(x_name) print(class(x)) return(NULL) } dispatch_fun <- function(x){ myfun2(unlist(x), names(x)) } a_ply(df, 2, dispatch_fun) ## [1] "Using factor method" ## [1] "f1" ## [1] "factor"

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