R中集合内的名称列 [英] Name columns within aggregate in R

问题描述

我知道我可以在汇总数据后*重命名列：

I know I can *re*name columns after I aggregate the data:

blubb <- aggregate(dat$two ~ dat$one, ...)
colnames(blubb) <- c("One", "Two")

这没错。但是，有一种方法可以一次性汇总和命名列吗？像这样：

Nothing wrong with that. But is there a way to aggregate and name the columns in one go? Sort of like:

blubb <- aggregate( ... , cols = c("One", "Two"))

以某种方式捕获原始列名并做特别好（且防错字）例如：

It would be escpecially nice (and typo-proof) to somehow catch the original column names and do like:

blubb <- aggregate( ... , cols = c(name_of_dat$one, name_of_dat$two."_Mean"))

推荐答案

您可以使用 setNames 如下：

blubb <- setNames(aggregate(dat$two ~ dat$one, ...), c("One", "Two"))

或者，可以绕过光滑的公式方法，并使用如下语法：

Alternatively, you can bypass the slick formula method, and use syntax like:

blubb <- aggregate(list(One = dat$one), list(Two = dat$two), ...)

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更新

此更新只是为了帮助您开始自己开发解决方案。

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Update

This update is to just help get you started on deriving a solution on your own.

如果您检查 stats ::: aggregate.formula 的代码，则会看到到结尾的以下几行：

If you inspect the code for stats:::aggregate.formula, you'll see the following lines towards the end:

if (is.matrix(mf[[1L]])) {
    lhs <- as.data.frame(mf[[1L]])
    names(lhs) <- as.character(m[[2L]][[2L]])[-1L]
    aggregate.data.frame(lhs, mf[-1L], FUN = FUN, ...)
}
else aggregate.data.frame(mf[1L], mf[-1L], FUN = FUN, ...)

如果要做的就是附加函数名对于汇总的变量，也许可以将其更改为：

If all that you want to do is append the function name to the variable that was aggregated, perhaps you can change that to something like:

if (is.matrix(mf[[1L]])) {
  lhs <- as.data.frame(mf[[1L]])
  names(lhs) <- as.character(m[[2L]][[2L]])[-1L]
  myOut <- aggregate.data.frame(lhs, mf[-1L], FUN = FUN, ...)
  colnames(myOut) <- c(names(mf[-1L]), 
                       paste(names(lhs), deparse(substitute(FUN)), sep = "."))
}
else {
  myOut <- aggregate.data.frame(mf[1L], mf[-1L], FUN = FUN, ...)
  colnames(myOut) <- c(names(mf[-1L]), 
                       paste(strsplit(gsub("cbind\\(|\\)|\\s", "", 
                                           names(mf[1L])), ",")[[1]],
                             deparse(substitute(FUN)), sep = "."))
} 
myOut

这基本上是使用 deparse（substitute（FUN）） FUN 输入的值。 c $ c>，因此您可以修改函数以接受自定义后缀，甚至可以接受后缀向量。可以通过一些工作对此进行一些改进，但是我不会这样做！

This basically captures the value entered for FUN by using deparse(substitute(FUN)), so you can probably modify the function to accept a custom suffix, or perhaps even a vector of suffixes. This can probably be improved a bit with some work, but I'm not going to do it!

这里是一个要点（应用了此概念），创建了一个名为 myAgg的函数。

Here is a Gist with this concept applied, creating a function named "myAgg".

以下是一些示例输出，仅包含结果列名称 ：

Here is some sample output of just the resulting column names:

> names(myAgg(weight ~ feed, data = chickwts, mean))
[1] "feed"        "weight.mean"
> names(myAgg(breaks ~ wool + tension, data = warpbreaks, sum))
[1] "wool"       "tension"    "breaks.sum"
> names(myAgg(weight ~ feed, data = chickwts, FUN = function(x) mean(x^2)))
[1] "feed"                         "weight.function(x) mean(x^2)"

请注意，仅聚合变量名称会更改。但也请注意，如果您使用自定义函数，则会得到一个非常奇怪的列名！

Notice that only the aggregated variable name changes. But notice also that if you use a custom function, you'll end up with a really strange column name!

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