迭代列表中的键/值对（）

I'd like to know how I can iterate over a key/value pair from a list object in R, like the example below:

我想知道如何迭代R中列表对象的键/值对，如下例所示：

toto <- list(a="my name is",b="I'm called",c="name:")
myfun <- function(key,value) paste(value,key)
for( key in names(toto) ) toto[key] <- myfun(key,toto[[key]])

Is there a way to avoid the for loop (using lapply() or such). Would it be faster?

有没有办法避免for循环（使用lapply（）或类似）。会更快吗？

Thanks!

谢谢！

2 个解决方案

#1

The best solution of all is to simply call paste directly without a loop (it's vectorized already):

最好的解决方案就是直接调用paste而不需要循环（它已经向量化了）：

> paste(toto, names(toto))
[1] "my name is a" "I'm called b" "name: c"

A similar question previously asked on R-Help, with several creative solutions. lapply cannot show the names within the function. This function was provided by Romain Francois based on something by Thomas Lumley:

之前在R-Help上提出的一个类似问题，有几个创意解决方案。 lapply无法显示函数内的名称。这个功能是由Romain Francois根据Thomas Lumley的一些东西提供的：

yapply <- function(X,FUN, ...) { 
  index <- seq(length.out=length(X)) 
  namesX <- names(X) 
  if(is.null(namesX)) 
    namesX <- rep(NA,length(X))

  FUN <- match.fun(FUN) 
  fnames <- names(formals(FUN)) 
  if( ! "INDEX" %in% fnames ){ 
    formals(FUN) <- append( formals(FUN), alist(INDEX=) )   
  } 
  if( ! "NAMES" %in% fnames ){ 
    formals(FUN) <- append( formals(FUN), alist(NAMES=) )   
  } 
  mapply(FUN,X,INDEX=index, NAMES=namesX,MoreArgs=list(...)) 
}

Here's an example of usage:

这是一个用法示例：

> yapply(toto, function( x ) paste(x, NAMES) )
             a              b              c 
"my name is a" "I'm called b"      "name: c"

#2

This should do it for you:

这应该为你做：

do.call(paste, list(toto, names(toto) ))

#1