For doing cross validation is it the parameter x which has to be used? Or is it some other parameter? I am confused. For doing 10 cross validation -x 10 will be fine.
Also in SVM light how to generate ROC curve. How to change threshold values in SVM?
No, x can allow only two option 0 and 1. For 10 fold cross-validation you have to divide your data in 10 set, then make training set and test set. If you want automatic then you can do this job in Rapidminer, Weka and R.
For ROC curve you can use SPSS or ROCR (in R), they just need SVM predicted score and it's real value (i.e. class tag for classification or real value for regression). You can also make ROC curve in Excel but it's not easy.
Thanx for the reply. Manually I have done it in SVM and in Weka also I have done it. I thought there was some parameter with which we could do in SVM
How to automate the same with Rapidminer and R?? SHould I write program????
REg ROC I have done in weka and excel. But in SVM can we do with the predicted score. How do we change threshold values to generate different values to draw curve. I am confused in that.
Rapidminer is just like Weka (even it is using Weka in background), for R you can read this paper "http://www.jstatsoft.org/v15/i09/paper"
Regarding ROCR and SPSS you don't bother about threshold software have inbuild capability to handle everything. Just you have to provide your data :
Class Prediction
+1 0.001
-1 -0.002
+1 0.74
-1 -0.03
Here 1st column is your class tag and second is svm score. for ROCR you can read http://rocr.bioinf.mpi-sb.mpg.de/ROCR.pdf".
Hi
just in case you want to try an alternative, we have binding libsvm to an open source library that allows you to plots directly a ROC curve for instance.
Example to plot a ROC:
http://www.idiap.ch/software/bob/docs/nightlies/last/bob/sphinx/html/TutorialsPerformance.html
Example to use SVM:
http://www.idiap.ch/software/bob/docs/nightlies/last/bob/sphinx/html/TutorialsMachine.html#support-vector-machines
The bob project main page: http://idiap.github.com/bob/
Thanx Mr Sebastien. Seems to be helpful. I will definitely try it out.
Sir, I downloaded bob.zip. Seems 2 b confused in installing the same. Cant find any setup file. I am using Windows 7 .
We have not tested bob on Windows yet. It is not supported for the moment.
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