仅在添加数字时将 NA 视为零 [英] Treat NA as zero only when adding a number

问题描述

计算两个数据表之和时，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 替换所有 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

这是如何在 R 中完成的?

How is this done in R?

更新:删除了 dt1 中的错字

推荐答案

你可以定义你自己的函数来做你想做的事情

You can define your own function to act as you want

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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