如何使用带有 dplyr 的列索引对选定列进行逐行求和? [英] How to do rowwise summation over selected columns using column index with dplyr?

问题描述

在 dplyr 中，如何对选定的列进行行求和(使用列索引)?

In dplyr, how do you perform rowwise summation over selected columns (using column index)?

这不起作用

> iris  %>% mutate(sum=sum(.[1:4])) %>% head
  Sepal.Length Sepal.Width Petal.Length Petal.Width Species    sum
1          5.1         3.5          1.4         0.2  setosa 2078.7
2          4.9         3.0          1.4         0.2  setosa 2078.7
3          4.7         3.2          1.3         0.2  setosa 2078.7
4          4.6         3.1          1.5         0.2  setosa 2078.7
5          5.0         3.6          1.4         0.2  setosa 2078.7
6          5.4         3.9          1.7         0.4  setosa 2078.7

我可以做以下，但不漂亮

I can do the following, but it's not beautiful

> iris %>% mutate(index=1:n()) %>%  
                gather("param", "value", 1:4)  %>% 
                group_by(index) %>% 
                mutate(sum=sum(value)) %>% 
                spread(param, value) %>% select(-index)
Source: local data frame [150 x 6]

   Species  sum Sepal.Length Sepal.Width Petal.Length Petal.Width
1   setosa 10.2          5.1         3.5          1.4         0.2
2   setosa  9.5          4.9         3.0          1.4         0.2
3   setosa  9.4          4.7         3.2          1.3         0.2
4   setosa  9.4          4.6         3.1          1.5         0.2
5   setosa 10.2          5.0         3.6          1.4         0.2
6   setosa 11.4          5.4         3.9          1.7         0.4
7   setosa  9.7          4.6         3.4          1.4         0.3
8   setosa 10.1          5.0         3.4          1.5         0.2
9   setosa  8.9          4.4         2.9          1.4         0.2
10  setosa  9.6          4.9         3.1          1.5         0.1
..     ...  ...          ...         ...          ...         ...

有没有在语法上更好的方法来实现这一点?

Is there more syntactically nicer way to achieve this?

它与其他问题不同，因为我想对使用列索引选择的列进行逐行操作"

It's different from other questions, because I want to do rowwise operation on the columns selected by using column indices"

推荐答案

正如评论中所说，您可以通过以下方式完成您的任务:

As already said in the comment, you can accomplish your task with:

iris %>% mutate(sum=Reduce("+",.[1:4]))

在这种情况下，基本的 rowSums 也有效:

In this case also the base rowSums works:

iris$sum<-rowSums(iris[,1:4])

这篇关于如何使用带有 dplyr 的列索引对选定列进行逐行求和?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！