[R] problems subsetting

[David Winsemius]

On Nov 18, 2010, at 10:42 AM, Martin Tomko wrote:

> Thanks Steve, that explains it... Unfortunately, I did nto get that  
> from my R docs...
>
> I am still searching for a solution for matching the entries in my  
> matrix by matching the rownames to the entires in a subset I got  
> using Gerrit's method.

OK. Looking back at your original question it appears you are  
confusing the actions of "&" and "|" when setting up selection  
criteria. It may sound strange but if you want the union of the group  
that is A and the group the is B then the criteria needs to be A | B ,  
not A & B.


So your original operation should have been:

subset1<-subset1[ subset1$Class == 1 | subset1$Type == 1 |  
subset1$Category == 1, ]

-- 
David.

>
> Any idea?
> Thanks
> Martin
>
> On 11/18/2010 4:35 PM, Steve Lianoglou wrote:
>> Hi,
>>
>> On Thu, Nov 18, 2010 at 10:25 AM, Martin Tomko<martin.tomko at geo.uzh.ch 
>> >  wrote:
>>
>>> Hi Gerrit,
>>> indeed, that works. Excellent tip!
>>>
>>> For reference, I did this:
>>>
>>> subset1<-subset(summarystats,(Type==1)&(Class==1)&(Category==1))
>>>
>>> I am still not totally sure when one uses "&" amd when"&&"  - I  
>>> was under
>>> the impression that&&  stands for logical AND....
>>>
>> If you can't find the appropriate documentation, try to experiment in
>> your workspace:
>>
>> R>  c(TRUE, TRUE, FALSE, TRUE)&  c(FALSE, TRUE, TRUE, TRUE)
>> [1] FALSE  TRUE FALSE  TRUE
>>
>> R>  c(TRUE, TRUE, FALSE, TRUE)&&  c(FALSE, TRUE, TRUE, TRUE)
>> [1] FALSE
>>
>> The single logical operators (&  , |) run over the entire length of
>> your logical vectors.
>> The doubles (&&, ||) just evaluate the first element of the vectors,
>> and ignore the rest.
>>
>>
>
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David Winsemius, MD
West Hartford, CT