如何按R中的分组列求和？ [英] How to sum by grouped columns in R?

问题描述

这是我的输入。具有n列的数据框，以及将每个ID分配给组的辅助数据框。

This is my input. A dataframe with n columns, and an auxiliary dataframe that assigns each id to a group.

df <- data.frame(
  a1 = c(1,2,3), 
  a2 = c(2,3,4), 
  b1 = c(4,5,6), 
  b2 = c(5,6,7)
)
aux <- data.frame(
  id = c("a1", "a2", "b1", "b2"),
  group = c("a", "a", "b", "b")
)

获得此输出的通用方法是什么？ （求和a1 + a2和b1 + b2）

What's a generalizable way to get to this output? (summing a1 + a2, and b1 + b2)

desired_output <- data.frame(
  a = c(3,5,7),
  b = c(9,11,13)
)

我尝试使用 dplyr :: group_by 和 tidyr :: unite ，但是我没有

I've tried using dplyr::group_by and tidyr::unite, but I haven't gotten it to work yet.

推荐答案

为了避免拆分数据帧并通过代码传递较长的数据帧列表，您可以使用以下索引：

In order to avoid having to split data frames and pass long lists of data frames through your code, you can just work with the indices:

cols <- split(aux$id, aux$group)

data.frame(lapply(cols, function(i) rowSums(df[i])))

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