只有在添加数字时，才将NA视为零 [英] Treat NA as zero only when adding a number

问题描述

计算两个数据表的总和时， NA + n = NA 。

When calculating the sum of two data tables, NA+n=NA.

> dt1 <- data.table(Name=c("Joe","Ann"), "1"=c(0,NA), "2"=c(3,NA))
> dt1
   Name  1  2
1:  Joe  0  3
2:  Ann NA NA
> dt2 <- data.table(Name=c("Joe","Ann"), "1"=c(0,NA), "2"=c(2,3))
> dt2
   Name  1 2
1:  Joe  0 2
2:  Ann NA 3
> dtsum  <- rbind(dt1, dt2)[, lapply(.SD, sum), by=Name]
> dtsum
   Name  1  2
1:  Joe  0  5
2:  Ann NA NA

我不想用0代替所有NA。我想要的是 NA + NA = NA 和 NA + n = n 以获得以下结果：

I don't want to substitute all NA's with 0. What I want is NA+NA=NA and NA+n=n to get the following result:

   Name  1  2
1:  Joe  0  5
2:  Ann NA  3

在R中如何做？

UPDATE：在dt1中删除拼写错误

推荐答案

plus <- function(x) {
 if(all(is.na(x))){
   c(x[0],NA)} else {
   sum(x,na.rm = TRUE)}
 }


rbind(dt1, dt2)[,lapply(.SD, plus), by = Name]

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