@scikit-learn developers:

Hum...
http://www.flickr.com/photos/scriptingnews/3503448168/sizes/o/in/photostream/

The situation is that the authors of libSVM have chosen a solution that
leads to inconsistent estimator with bad statistical properties, but
works well on many datasets. I think it is wrong, but then, I am worried
that this might be a battle that we might not win.

On the one hand, we really cannot have C the way the libSVM guy have
defined it, because parameter setting by cross-validation will not work.
On the other hand, it is clear that people keep tripping over this
difference. Should we introduce a different name, that way it forces
people to read the docs?

We've been going round and round with regards to this issue for a while
:)

G

On Tue, Apr 17, 2012 at 12:39:04PM +0300, Dimitrios Pritsos wrote:

> Hello G,

> Yes you are right the scale_C should be False for working as expected.

> Great because I prefer to work with the latest version.

> Thank you G

> Dimitrios



> On 04/17/2012 12:13 PM, Dimitrios Pritsos wrote:

> > Ok I will do that now and I will let you know in 45 min

> > On 04/17/2012 12:10 PM, Gael Varoquaux wrote:
> >> On Tue, Apr 17, 2012 at 12:08:46PM +0300, Dimitrios Pritsos wrote:
> >>> I was running a test using SVC(c=1, kernel='linear') and I found that
> >>> for the latest version of sklearn the results are WRONG!
> >> What does 'wrong' mean?

> >> Something that changed in the scikit, is that the 'c' is scaled by the
> >> number of samples by default. Try with 'scale_C=False', and tells us if
> >> your results are now 'RIGHT' :).

> >> G

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-- 
    Gael Varoquaux
    Researcher, INRIA Parietal
    Laboratoire de Neuro-Imagerie Assistee par Ordinateur
    NeuroSpin/CEA Saclay , Bat 145, 91191 Gif-sur-Yvette France
    Phone:  ++ 33-1-69-08-79-68
    http://gael-varoquaux.info            http://twitter.com/GaelVaroquaux

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