R help - Oct 2008 - tune function using sigmoid and polynomial kernels

Hello,
When i use tune svm with sigmoid oy polynomial kernels to optimize
Cost/gamma/coef0 (sigmoid) or cost/gamma/coef0/degree (polynomial)
parameters, i can't get a summary of the best parameters. instead I got this
result:
  dummyparameter
1              0

I use the following command line (7 fold cross validation):
tunesv <- tune(svm, x, y, kernel="sigmoid", coef0= -1:1,
gamma=10^(-6:-2),
cost=10^(0:3), tunecontrol=tune.control(sampling="cross", cross=7))

When i use a similar function for radial kernels, I get the best gamma and
cost parameters.

Thanks for  your help.

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