[R] SVM coefficients

[Achim Zeileis]

On Mon, 31 Aug 2009, Noah Silverman wrote:

> Steve,
>
> That doesn't work.
>
> I just trained an SVM with 80 variables.
> svm_model$coefs gives me  a list of 10,000 items.  My training set is 30,000 
> examples of 80 variables, so I have no idea what the 10,000 items represent.

Presumably, the coefficients of the support vectors times the training 
labels, see help("svm", package = "e1071"). See also
   http://www.jstatsoft.org/v15/i09/
for some background information and the different formulations available.

> There should be some attribute that lists the "weights" for each of the 80 
> variables.

Not sure what you are looking for. Maybe David, the author auf svm() (and 
now Cc), can help.
Z

> --
> Noah
>
> On 8/30/09 7:47 PM, Steve Lianoglou wrote:
>> Hi,
>> 
>> On Sun, Aug 30, 2009 at 6:10 PM, Noah Silverman<noah at smartmediacorp.com> 
>> wrote:
>> 
>>> Hello,
>>> 
>>> I'm using the svm function from the e1071 package.
>>> 
>>> It works well and gives me nice results.
>>> 
>>> I'm very curious to see the actual coefficients calculated for each input
>>> variable.  (Other packages, like RapidMiner, show you this automatically.)
>>> 
>>> I've tried looking at attributes for the model and do see a "coefficients"
>>> item, but printing it returns an NULL result.
>>> 
>> Hmm .. I don't see a "coefficients" attribute, but rather a "coefs"
>> attribute, which I guess is what you're looking for (?)
>> 
>> Run "example(svm)" to its end and type:
>> 
>> R>  m$coefs
>>               [,1]
>>   [1,]  1.00884130
>>   [2,]  1.27446460
>>   [3,]  2.00000000
>>   [4,] -1.00000000
>>   [5,] -0.35480340
>>   [6,] -0.74043692
>>   [7,] -0.87635311
>>   [8,] -0.04857869
>>   [9,] -0.03721980
>> [10,] -0.64696793
>> [11,] -0.57894605
>> 
>> HTH,
>> 
>> -steve
>> 
>> 
>
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