调用函数时设置列名 [英] Set column names while calling a function

问题描述

考虑我们有一个数字数据框 foo 并且想要找到每两列的总和:

Consider we have a numeric data.frame foo and want to find the sum of each two columns:

foo <- data.frame(x=1:5,y=4:8,z=10:14, w=8:4)
bar <- combn(colnames(foo), 2, function(x) foo[,x[1]] + foo[,x[2]])
bar
#     [,1] [,2] [,3] [,4] [,5] [,6]
#[1,]    5   11    9   14   12   18
#[2,]    7   13    9   16   12   18
#[3,]    9   15    9   18   12   18
#[4,]   11   17    9   20   12   18
#[5,]   13   19    9   22   12   18

一切都很好，除了 bar 中缺少的列名.我希望 bar 的列名显示 foo 中的相关列，例如在这个例子中:

Everything is fine, except the column names that are missing from bar. I want column names of bar to show the related columns in foo, for instance in this example:

colnames(bar) <- apply(combn(colnames(foo),2), 2, paste0,collapse="")
colnames(bar)
#[1] "xy" "xz" "xw" "yz" "yw" "zw"

这很简单，但我想在同一个 bar <- combn(...) 命令中执行列标记.有吗?

This is simple, but I want to perform column labeling in the same bar <- combn(...) command. Is there anyway?

推荐答案

这是可能的，但它会混淆您的代码.此处简洁与清晰之间的权衡非常重要.

It is possible, but it obfuscates your code. The tradeoff between brevity and clarity here is acute.

要了解它是如何工作的，我参考了这个问题.

To understand how it works, I reference this question.

colnames(x) <- y

内部改写为

x <- `colnames<-`(x,y)

然后您可以自己进行翻译.

You can then do the translation yourself.

bar <- `colnames<-`(combn(colnames(foo), 2, function(x) foo[,x[1]] + foo[,x[2]]),
                    apply(combn(colnames(foo),2), 2, paste0,collapse=""))

然而，在许多情况下，以这种方式折叠代码行所需的心理和句法体操是不值得的.多条线往往更清晰.

In many cases, however, it's not worth the mental and syntactic gymnastics required to collapse lines of code in this way. Multiple lines tend to be clearer to follow.

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