[R] Forumla format?

[Steve Lianoglou]

Hi,

On Jul 27, 2009, at 3:47 PM, Noah Silverman wrote:

> Hi,
>
> I'm not sure that would work for the "formula" format of an SVM  
> function.
>
> the idea is normally
>
> svm(label ~ c1 + c2 +c3, data=mydata);
>
> It doesn't work to say
>
> svm(label ~ -c(22,23,24), data=mydata)

You're quite right. Sorry, I misunderstood the question ... I'm  
actually not sure if/how you could do that as I don't use the formula  
"formulation" too much.

Is it possible to build up your formula as a string, and then convert  
to formula w/ as.formula?

ie.

f <- as.formula(sprintf('label ~ %s', paste(colnames(my.data)[- 
c(22,23,24), collapse=" + "))

Then use `f` in your call to svm? Maybe?

-steve

>
>
> On 7/27/09 12:17 PM, Steve Lianoglou wrote:
>>
>> Hi,
>>
>> On Jul 27, 2009, at 3:01 PM, Noah Silverman wrote:
>>
>>> Hi,
>>>
>>> Quick question.
>>>
>>> I'm working on training an SVM.
>>>
>>> I have a dataframe with about 50 columns.  I want to train on 46  
>>> of them.
>>>
>>> Is there a way to say "All except columns 22,23,25 and 31"?
>>
>> Assume your dataframe is called "my.data":
>>
>> my.data[,-c(22,23,25,31)]
>>
>> Returns the data.frame w/o columns 22,23,25 and 31.
>>
>> -steve
>>
>>> It would be nice to not have to do +c1 +c2 +c3 +c4, etc for all 48  
>>> columns.
>>
>> Yes, it is nice, isn't it? :-)
>>
>> -steve
>>
>> -- 
>> Steve Lianoglou
>> Graduate Student: Computational Systems Biology
>>   |  Memorial Sloan-Kettering Cancer Center
>>   |  Weill Medical College of Cornell University
>> Contact Info: http://cbio.mskcc.org/~lianos/contact
>>

--
Steve Lianoglou
Graduate Student: Computational Systems Biology
   |  Memorial Sloan-Kettering Cancer Center
   |  Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact