在data.table中创建新列 [英] Creating new columns in data.table

问题描述

R的data.table中有几列(字面上)分别命名为A1，A2，A3，... A50.不幸的是，我的表中的列不是按字母顺序排列的.

I have several columns (literally) named A1, A2, A3, ... A50 in a data.table in R. Unfortunately, columns in my table are not arranged alphabetically.

我想创建一个名为sumA的新列，其中将包含A1 + A2 + ... + A50.

I want to create a new column named sumA, which will contain A1 + A2 + ... + A50.

什么是简单(而不乏味)的方法?

What's a simple (and not tedious) way of doing this?

推荐答案

这里是 Reduce 和 +

library(data.table)
dt[, sumA := Reduce("+", .SD)]

如果还有其他列，即数据集中除"A1:A50"以外的其他列，请使用 .SDcols 指定要选择的列

If there are other columns i.e. columns other than 'A1:A50' in the dataset, use the .SDcols to specify the columns to select

dt[, sumA := Reduce("+", .SD), .SDcols = paste0("A", 1:50)]

或者如@Arun所述，如果列是有序的，则可以使用:来选择列

Or as @Arun mentioned, if the columns are ordered, then : can be used to select the column

dt[, sumA := Reduce("+", .SD), .SDcols = A1:A50]

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