In case it may help any of you, I simply ended up using linearSVC.
Its .decision_function() gives one value for each class and compatible with
.predict() function!
Plus, it turned out to be faster than svm.svc (as always) and more accurate
for my dataset.
Thanks again for your help
On Tue, May 7, 2013 at 5:03 PM, Bilal Dadanlar <[email protected]>wrote:
> Thank you all. I havent thought of regression before. but i'll give it a
> try.
>
> afaik, platt scaling also use .decision_function() values, which gives
> N*(N-1)/2 signed distance for each class pair (Ni,Nj).
> but I'm not sure if i can create a better ranking according to them.
>
>
>
> On Tue, May 7, 2013 at 1:09 PM, Peter Prettenhofer <
> [email protected]> wrote:
>
>>
>>
>>
>> 2013/5/7 Lars Buitinck <[email protected]>
>>
>>> 2013/5/7 Peter Prettenhofer <[email protected]>:
>>> > Do you need probabilities? You could just use the signed distance to
>>> each
>>> > OVA hyperplane (via ``clf.decision_function()``) to rank the classes.
>>> Maybe
>>> > the platt-scaling screws up here...
>>>
>>> The more I find out about Platt scaling in LibSVM, the more I'm
>>> inclined to stay away from it.
>>>
>>> > You could also look at Mathieu's "lightning" project
>>> > https://github.com/mblondel/lightning - it features multinomial
>>> logistic
>>> > regression which might give better calibrated probabilities than platt
>>> > scaling...
>>>
>>> Or our own LogisticRegression. It cuts some corners, but sometimes
>>> it's good enough.
>>>
>>
>> Right, it should give you the same ordering as ``decision_function``
>> (just normalized).
>>
>>
>>>
>>> --
>>> Lars Buitinck
>>> Scientific programmer, ILPS
>>> University of Amsterdam
>>>
>>>
>>> ------------------------------------------------------------------------------
>>> Learn Graph Databases - Download FREE O'Reilly Book
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>>
>>
>>
>> --
>> Peter Prettenhofer
>>
>>
>> ------------------------------------------------------------------------------
>> Learn Graph Databases - Download FREE O'Reilly Book
>> "Graph Databases" is the definitive new guide to graph databases and
>> their applications. This 200-page book is written by three acclaimed
>> leaders in the field. The early access version is available now.
>> Download your free book today! http://p.sf.net/sfu/neotech_d2d_may
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>>
>>
>
>
> --
> Bilal Dadanlar
> cimri.com | Yazılım Mühendisi
>
--
Bilal Dadanlar
cimri.com | Yazılım Mühendisi
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