
#1




Libsvm
The LIBSVM package is new to me, as I suppose it is for many of us. I also have very little experience with working with "black box" packages. I have difficulty trusting my results. I think it might be useful to have a thread where we could share our experience and help each other learn LIBSVM.

#2




Re: Libsvm
I currently struggle to understand how to use the build in crossvalidation capability. I don't understand yet what exactly I don't understand, but I definitely don't understand something.
Specifically, when using 1vs1 classification on the digit set, I get some result for E_in error, that is close to E_out error. But whatever my parameters, the crossvalidation accuracy on the problem gives me 99.8% accuracy, which is way higher than E_in or E_out. Any ideas? Code:
cva = svmtrain(Y, X, 't 1 d 2 g 1 r 1 v 10 c 0.01' ); 
#3




Re: Libsvm
I am running libsvm from the command line executables. The cross validation accuracy is shown in 4 decimal places for different values of C. I also used the command line tool to scale my input data, wonder if that mattered.

#4




Re: Libsvm
Quote:
I have now applied data scaling (my own version) and this did result in discrete cva measures for the various C values, although cva does seem high still Last edited by alfansome; 05262012 at 10:18 AM. Reason: updated 
#5




Re: Libsvm
I'm new to libsvm (as I'm sure many other students), so my first question is how do I get E_in from svm_train?
I'm using the Java version. Thanks for any pointers. Code:
options: s svm_type : set type of SVM (default 0) 0  CSVC 1  nuSVC 2  oneclass SVM 3  epsilonSVR 4  nuSVR t kernel_type : set type of kernel function (default 2) 0  linear: u'*v 1  polynomial: (gamma*u'*v + coef0)^degree 2  radial basis function: exp(gamma*uv^2) 3  sigmoid: tanh(gamma*u'*v + coef0) 4  precomputed kernel (kernel values in training_set_file) d degree : set degree in kernel function (default 3) g gamma : set gamma in kernel function (default 1/num_features) r coef0 : set coef0 in kernel function (default 0) c cost : set the parameter C of CSVC, epsilonSVR, and nuSVR (default 1) n nu : set the parameter nu of nuSVC, oneclass SVM, and nuSVR (default 0.5) p epsilon : set the epsilon in loss function of epsilonSVR (default 0.1) m cachesize : set cache memory size in MB (default 100) e epsilon : set tolerance of termination criterion (default 0.001) h shrinking : whether to use the shrinking heuristics, 0 or 1 (default 1) b probability_estimates : whether to train a SVC or SVR model for probability estimates, 0 or 1 (default 0) wi weight : set the parameter C of class i to weight*C, for CSVC (default 1) v n : nfold cross validation mode q : quiet mode (no outputs) 
#6




Re: Libsvm
Quote:
did you mean that 0,2% (10099,8) is higher than your E_in and E_out? Because Accuracy = 100%  E, right? 
#7




Re: Libsvm
Maybe I should create a separate thread for this, but I'm still stuck at trying to figure out how to get libsvm to compute E_in.
Here is a typical output (I use the commandline Java tools): Code:
optimization finished, #iter = NNNN nu = XXXXXXX obj = YYYYY, rho = ZZZZZ nSV = A, nBSV = B Total nSV = C Is there a magical switch that I am missing? Thanks. Samir 
#8




Re: Libsvm
Quote:
you just have to set computed model to a variable: Code:
MyModel = svmtrain(y,X,[options]) Code:
[predicted_labels, accuracy] = svmpredict(y_test, X_test, MyModel) PS I assume using Matlab/Octave, but for other interfaces procedures is the same, difference only in sintax, I believe. 
#9




Re: Libsvm
Thanks ... I'm using Java commandline version (hoping to get away without having to write any code in this homework).
I'll try to figure out how to do what you're suggesting in Java. Samir 
#10




Re: Libsvm
Tried to use libsvm in Windows as per the Youtube video. However when I try to run svmtrain.exe on the training data a1a.train it comes back with the message "cannot open the input file".
This course was going great till HW6. After that, it has become a test of working with software packages and dealing with error messages. 
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