Hi, Uwe, Thanks for the reply!! I have 87 observations in total. If this amount causes the different best.parameters, is there a better way than cross validation to tune them?
Thank you so much for the help! Best Regards, Maggie On Dec 27, 2007 6:17 PM, Uwe Ligges <[EMAIL PROTECTED]> wrote: > > > Maggie Wang wrote: > > Hi, > > > > I run the following tuning function for svm. It's very strange that > every > > time i run this function, the best.parameters give different values. > > > > [A] > > > >> svm.tune <- tune(svm, train.x, train.y, > > > > validation.x=train.x, validation.y=train.y, > > > > ranges = list(gamma = 2^(-1:2), > > > > cost = 2^(-3:2))) > > > > > > > > # where train.x and train.y are matrix specified. > > > > > > > > # output command: > > > > > > > >> svm.tune$best.parameters$cost > > > >> svm.tune$best.parameters$gamma > > > > > > > > result: > > > > cost gamma > > 0.25 4.00 > > > > > > > > run A again: > > > > cost gamma > > 1 4 > > > > > > > > again: > > > > cost gamma > > 0.25 4.00 > > > > > > > > The result is so unstable, if it varies so much, why do we need to tune? > Do > > you know if this behavior is normal? Can we trust the best.parametersfor > > prediction? > > I guess you do not have really many observations in your dataset. Then > it highly depends ion the cross validation sets which parameter is best. > And therefore you get quite different results. > > Uwe Ligges > > > > > > > > > Thank you so much to help out!! > > > > > > > > Best Regards, > > > > Maggie > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > R-help@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<http://www.r-project.org/posting-guide.html> > > and provide commented, minimal, self-contained, reproducible code. > [[alternative HTML version deleted]] ______________________________________________ R-help@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.
