[R] Problem Subsetting Rows that Have NA's

BooBoo booboo at gforcecable.com
Wed Oct 25 15:57:37 CEST 2017

```On 10/25/2017 4:38 AM, Ista Zahn wrote:
> 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
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