拆分`...`参数并分配给多个函数-Splitup`…`argumentsanddistributetomultiplefunctions

23  

Separate Lists If you really want to pass different sets of parameters to different functions then it's probably cleaner to specify separate lists:

单独的列表如果您确实想要将不同的参数集传递给不同的函数，那么指定单独的列表可能更简洁：

foo <- function(x, y, sum = list(), grep = list()) {
 list(sum = do.call("sum", c(x, sum)), grep = do.call("grep", c("abc", y, grep)))
}

# test

X <- c(1:5, NA, 6:10)
Y <- "xyzabcxyz"
foo(X, Y, sum = list(na.rm = TRUE), grep = list(value = TRUE))

## $sum
## [1] 55
## 
## $grep
## [1] "xyzabcxyz"

Hybrid list / ... An alternative is that we could use ... for one of these and then specify the other as a list, particularly in the case that one of them is frequently used and the other is infrequently used. The frequently used one would be passed via ... and the infrequently used via a list. e.g.

混合列表/ ...另一种选择是我们可以使用...作为其中之一，然后将另一个指定为列表，特别是在经常使用其中一个而另一个不经常使用的情况下。经常使用的一个将通过...传递，并且通过列表不经常使用。例如

foo <- function(x, y, sum = list(), ...) {
 list(sum = do.call("sum", c(x, sum)), grep = grep("abc", y, ...))
}

foo(X, Y, sum = list(na.rm = TRUE), value = TRUE)

Here are a couple of examples of the hybrid approach from R itself:

以下是R本身的混合方法的几个例子：

i) The mapply function takes that approach using both ... and a MoreArgs list:

i）mapply函数使用...和MoreArgs列表的方法：

> args(mapply)
function (FUN, ..., MoreArgs = NULL, SIMPLIFY = TRUE, USE.NAMES = TRUE) 
NULL

ii) nls also takes this approach using both ... and the control list:

ii）nls也使用这两种方法和控制列表：

> args(nls)
function (formula, data = parent.frame(), start, cOntrol= nls.control(), 
    algorithm = c("default", "plinear", "port"), trace = FALSE, 
    subset, weights, na.action, model = FALSE, lower = -Inf, 
    upper = Inf, ...) 
NULL

12  

1. Why does grep error before sum?

   为什么总和之前的grep错误？

   See that sum is a lot more accommodating with its arguments:

   看到总和更适应其论点：

   X <- c(1:5, NA, 6:10)
   sum(X, na.rm = TRUE, value = TRUE)
   ## [1] 56
   

   It doesn't failed because it doesn't care about other named arguments, so the value = TRUE simplifies to just TRUE which sums to 1. Incidentally:

   它没有失败，因为它不关心其他命名参数，所以value = TRUE简化为TRUE，总和为1.顺便说一下：

   sum(X, na.rm = TRUE)
   ## [1] 55
   

2. How to split ... to different functions?

   如何拆分......到不同的功能？

   One method (that is very prone to error) is to look for the args for the target functions. For instance:

   一种方法（非常容易出错）是寻找目标函数的args。例如：

   foo <- function(x, y, ...){
       argnames <- names(list(...))
       sumargs <- intersect(argnames, names(as.list(args(sum))))
       grepargs <- intersect(argnames, names(as.list(args(grep))))
       list(sum = do.call(sum, c(list(x), list(...)[sumargs])),
            grep = do.call(grep, c(list("abc", y), list(...)[grepargs])))
   }
   

   This is prone to error anytime the arguments a function uses are not properly reported by args, such as S3 objects. As an example:

   只要args（例如S3对象）没有正确报告函数使用的参数，这就容易出错。举个例子：

   names(as.list(args(plot)))
   ## [1] "x"   "y"   "..." ""   
   names(as.list(args(plot.default)))
   ##  [1] "x"           "y"           "type"        "xlim"        "ylim"       
   ##  [6] "log"         "main"        "sub"         "xlab"        "ylab"       
   ## [11] "ann"         "axes"        "frame.plot"  "panel.first" "panel.last" 
   ## [16] "asp"         "..."         ""           
   

   In this case, you could substitute the appropriate S3 function. Because of this, I don't have a generalized solution for this (though I don't know that it does or does not exist).

   在这种情况下，您可以替换相应的S3函数。因此，我没有一个通用的解决方案（虽然我不知道它确实存在或不存在）。

0  

You can only pass the ... argument to another function, if that other function includes all named arguments that you pass to ... or if it has a ... argument itself. So for sum, this is no problem (args(sum) returns function (..., na.rm = FALSE)). On the other hand grep has neither na.rm nor ... as an argument.

您只能将...参数传递给另一个函数，如果该其他函数包含您传递给的所有命名参数...或者它本身具有...参数。所以总和来说，这没有问题（args（sum）返回函数（...，na.rm = FALSE））。另一方面，grep既没有na.rm也没有...作为论据。

args(grep)
# function (pattern, x, ignore.case = FALSE, perl = FALSE, value = FALSE, 
#     fixed = FALSE, useBytes = FALSE, invert = FALSE) 

This does not include ... and also does not include a named argument na.rm either. A simple solution is to just define your own function mygrep as follows:

这不包括......也不包括命名参数na.rm。一个简单的解决方案是只需定义自己的函数mygrep，如下所示：

mygrep <- function (pattern, x, ignore.case = FALSE, perl = FALSE, value = FALSE, 
                    fixed = FALSE, useBytes = FALSE, invert = FALSE, ...)
  grep(pattern, x, ignore.case, perl, value, fixed, useBytes, invert)

Then it seems to work:

然后它似乎工作：

foo <- function(x, y, ...){
  list(sum = sum(x, ...), grep = mygrep("abc", y, ...))
}
X <- c(1:5, NA, 6:10)
Y <- "xyzabcxyz"
foo(X, Y, na.rm = TRUE, value = TRUE)

# $sum
# [1] 56
# 
# $grep
# [1] "xyzabcxyz"