[R] how to choose cost in SVM analysis with kernlab

[Luigi Marongiu]

Dear all,
I have set a model for SVM analysis using laplacedot with the package
kernlab. I checked the classification error with a k-fold approach,
that is I analyzed 1/10 of the data ten times and averaged the error
(FalseNeg + FalsePos) / TOT. I tested different levels of cost C and
the results are:

C         error
0.01    0.106566
0.10    0.070798
0.50    0.000985
1.00    0.000556
2.50    0.000198
5.00    0.000079
7.50    0.000040
8.00    0.000040
8.50    0.000016
9.00    0.000008
9.50    0.000000
10.00  0.000000
10.50  0.000000
100.00 0.000000

Given that the purpose of the optimization is to minimize the error, a
C>=9 is therefore what I am looking for. But, if the model is too
stringent, then I will have problems with the future sets.
So what level should I set? My feeling is that C=1 is enough.
Is there a method within kernlab to maximize C (and gamma perhaps)
automatically?


-- 
Best regards,
Luigi