> On Oct 25, 2017, at 11:17 AM, David Winsemius <dwinsem...@comcast.net> wrote:
>
>
>> On Oct 25, 2017, at 6:57 AM, BooBoo <boo...@gforcecable.com> wrote:
>>
>> On 10/25/2017 4:38 AM, Ista Zahn wrote:
>>> On Tue, Oct 24, 2017 at 3:05 PM, BooBoo <boo...@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@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.
>>
>> I wanted to know if this was a bug so that I could report it if so. You say
>> it is not, so you answered my question. As far as me not reading the
>> documentation, I challenge anyone to read the cited help pages and predict
>> the observed behavior based on the information given in those pages.
>
> Some of us do share (or at least remember feeling) your pain. The ?Extract
> page is long and complex and there are several features that I find
> non-intuitive. But they are deemed desirable by others. I think I needed to
> read that page about ten times (with multiple different problems that needed
> explication) before it started to sink in. You are apparently on that same
> side of the split opinions on the feature of returning rows with logical NA's
> as I am. I've learned to use `which`, and I push back when the conoscienti
> says it's not needed.
horrible misspelling of cognoscenti
> After you read it a few more times you may come to a different opinion. Many
> people come to R with preconceived notions of what words like "equals" or
> "list" or "vector" mean and then complain about the documentation. You would
> be better advised to spend more time studying the language. The help pages
> are precise but terse, and you need to spend time with the examples and with
> other tutorial material to recognize the gotcha's.
>
> Here's a couple of possibly helpful rules regarding "[[" and "[" and logical
> indexing:
>
> Nothing _equals_ NA.
> Selection operations with NA logical index item return NA. (Justified as a
> warning feature as I understand it.)
> "[" always returns a list.
That's not true or even half true. "[" always returns a list if it's first
argument is a list and it only has two arguments.
If X is a list and you ask for X[vector] you get a list
If you ask for X[vector, ] you may get a list or a vector.
If you ask for X[two_column_matrix] you get a vector.
I should be flogged.
> "[[" returns only one thing, but even that thing could be a list.
Horribl;y imprecise.
> Generally you want "[[" if you plan on testing for equality with a vector.
Don't listen to me. Read ....
>
> The "R Inferno" by Burns is an effort to detail many more of the unexpected
> or irregular aspects of R (mostly inherited from S).
>
> --
> Best of luck in your studies.
>
>
>>
>> ______________________________________________
>> R-help@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.
>
> David Winsemius
> Alameda, CA, USA
>
> 'Any technology distinguishable from magic is insufficiently advanced.'
> -Gehm's Corollary to Clarke's Third Law
>
> ______________________________________________
> R-help@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.
David Winsemius
Alameda, CA, USA
'Any technology distinguishable from magic is insufficiently advanced.'
-Gehm's Corollary to Clarke's Third Law
______________________________________________
R-help@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.
