[R] problems subsetting

[Peter Ehlers]

On 2010-11-18 07:25, Martin Tomko 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....
>
This indicates that you haven't looked at (or absorbed) the
help page for logic operators. It's pretty well explained
there that both & and && perform AND, but the first is for
elementwise comparison which is what your application
clearly requires.

   -Peter Ehlers

> Thanks a lot.
>
>
> Martin
>
> On 11/18/2010 3:58 PM, Gerrit Eichner wrote:
>> Hello, Martin,
>>
>> as to your first problem, look at function subset(), and particularly
>> at its argument "subset".
>>
>> HTH,
>>
>> Gerrit
>>
>>
>> On Thu, 18 Nov 2010, Martin Tomko wrote:
>>
>>> Dear all,
>>> I have searched the forums for an answer - and there is plenty of
>>> questions along the same line - but none of the paproaches shown
>>> worked to my problem:
>>>
>>> I have a data frame that I get from a csv:
>>>
>>> summarystats<-as.data.frame(read.csv(file=f_summary));
>>>
>>> where I have the columns Dataset, Class, Type, Category,..
>>> Problem1:  I want to find a subset of this frame, based on values in
>>> multiple columns
>>> What I do currently is:
>>>
>>> subset1<- summarystats
>>> subset1<-subset1[subset1$Class == 1,]
>>> subset1<-subset1[subset1$Type == 1,]
>>> subset1<-subset1[subset1$Category == 1,]
>>>
>>> Now, this works, but is UGLY! I tried using "&&" or"&" , for
>>> isntance : subset1<-subset1[ (subset1$Class == 1)&&  (subset1$Category
>>> == 1),]
>>> but it returns an empty data frame.
>>>
>>> Anyway, the main problem is
>>> Problem2:
>>> I have a second data frame - a square matrix (rownames == colnames),
>>> distm:
>>>
>>> distm<-read.table(file=f_simmatrix, sep = ",");
>>> what I want is select ONLY the columns and rows entries matching the
>>> above subset1:
>>>
>>> subset2<-distm[subset1$Dataset,subset1$Dataset] returns a matrix of
>>> correct size, but with incorrect entries (established by visual
>>> inspection).
>>>
>>> this is the same as:
>>> selectedrows<-as.vector(subset1$Dataset)
>>> subset2<-distm[selectedrows,selectedrows]
>>>
>>> also verified using:
>>> rownames(subset2)%in% selectedrows
>>> [1] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
>>> FALSE
>>> [13] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
>>> FALSE FALSE
>>> [25] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
>>> FALSE FALSE
>>> [37] FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
>>>
>>> What am I missing?
>>>
>>> Thanks
>>> Martin
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> 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.
>>>
>>
>> ---------------------------------------------------------------------
>> AOR Dr. Gerrit Eichner               Mathematical Institute, Room 212
>> gerrit.eichner at math.uni-giessen.de   Justus-Liebig-University Giessen
>> Tel: +49-(0)641-99-32104          Arndtstr. 2, 35392 Giessen, Germany
>> Fax: +49-(0)641-99-32109        http://www.uni-giessen.de/cms/eichner
>> ---------------------------------------------------------------------
>>
>
>