[R] Problem Subsetting Rows that Have NA's

[Ista Zahn]

On Tue, Oct 24, 2017 at 3:05 PM, BooBoo <booboo at gforcecable.com> wrote:
> This has every appearance of being a bug. If it is not a bug, can someone
> tell me what I am asking for when I ask for "x[x[,2]==0,]". Thanks.

You are asking for elements of x where the second column is equal to zero.

help("==")

and

help("[")

explain what happens when missing values are involved. I agree that
the behavior is surprising, but your first instinct when you discover
something surprising should be to read the documentation, not to post
to this list. After having read the documentation you may post back
here if anything remains unclear.

Best,
Ista

>
>> #here is the toy dataset
>> x <- rbind(c(1,1),c(2,2),c(3,3),c(4,0),c(5,0),c(6,NA),
> +   c(7,NA),c(8,NA),c(9,NA),c(10,NA)
> + )
>> x
>       [,1] [,2]
>  [1,]    1    1
>  [2,]    2    2
>  [3,]    3    3
>  [4,]    4    0
>  [5,]    5    0
>  [6,]    6   NA
>  [7,]    7   NA
>  [8,]    8   NA
>  [9,]    9   NA
> [10,]   10   NA
>>
>> #it contains rows that have NA's
>> x[is.na(x[,2]),]
>      [,1] [,2]
> [1,]    6   NA
> [2,]    7   NA
> [3,]    8   NA
> [4,]    9   NA
> [5,]   10   NA
>>
>> #seems like an unreasonable answer to a reasonable question
>> x[x[,2]==0,]
>      [,1] [,2]
> [1,]    4    0
> [2,]    5    0
> [3,]   NA   NA
> [4,]   NA   NA
> [5,]   NA   NA
> [6,]   NA   NA
> [7,]   NA   NA
>>
>> #this is more what I was expecting
>> x[which(x[,2]==0),]
>      [,1] [,2]
> [1,]    4    0
> [2,]    5    0
>>
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.