用 R 对行求和? [英] Sum pairwise rows with R?

问题描述

我的意见是

 df1 <- data.frame(Row=c("row1", "row2", "row3", "row4", "row5"),
                   A=c(1,2,3,5.5,5), 
                   B=c(2,2,2,2,0.5),
                   C= c(1.5,0,0,2.1,3))

看起来像这样:

#  Row1 1   2   1.5
#  Row2 2   2   0
#  Row3 3   2   0
#  Row4 5.5 2   2.1
#  Row5 5   0.5 3

我想通过以下等式获得所有这些行对的总和.让我们说 Row1 和 Row2 对:我想将每一列的条目相乘并将它们相加成一个最终答案，例如 -

I want to get the sum of all these pairs of rows, with the following equation. Let's said for Row1 and Row2 pairs: I want to multiply each column's entry and sum them into one final answer, for example-

• Row1-Row2 的答案是 (1*2) + (2*2)+ (1.5 *0) = 6
• Row1-Row3 的答案是 (1*3) + (2*2) + (1.5*0) = 7

• Row1-Row2 answer is (1*2) + (2*2)+ (1.5 *0) = 6
• Row1-Row3 answer is (1*3) + (2*2) + (1.5*0) = 7

我想对每对行进行所有分析，并得到这样的结果数据框:

I want to do all analysis for each pairs of row and get a result data frame like this:

row1    row2    6
row1    row3    7
row1    row4    12.65
row1    row5    10.5
row2    row3    10
row2    row4    15
row2    row5    11
row3    row4    20.5
row3    row5    16
row4    row5    34.8

我怎样才能用 R 做到这一点?非常感谢您的意见.

How can I do this with R? Thanks a lot for comments.

推荐答案

1. 使用 combn 创建您需要的所有组合.t 用于按照您期望的格式转置矩阵.
2. 使用 apply 迭代在步骤 1 中创建的索引.请注意，我们使用负索引，因此我们不会尝试对 Row 列求和.
3. 将两个结果绑定在一起.

1. Create all the combinations you need with combn. t is used to transpose the matrix as you expect it to be formatted.
2. Use apply to iterate over the indices created in step 1. Note that we use negative indexing so we don't try to sum the Row column.
3. Bind the two results together.

`

ind <- t(combn(nrow(df1),2))
out <- apply(ind, 1, function(x) sum(df1[x[1], -1] * df1[x[2], -1]))
cbind(ind, out)

           out
[1,] 1 2  6.00
[2,] 1 3  7.00
[3,] 1 4 12.65
 .....

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