On Sat, Mar 17, 2012 at 11:55 PM, Mathieu Blondel <[email protected]> wrote:
>> The alpha specified this way could (should?) have the same name and
>> interpretation as the l2_regularization coefficient in the
>> SGDClassifier.
>
> Would you convert alpha into a C internal value or would you patch
> libsvm / liblinear to use alpha? I don't understand how the former
> would be different from the scale_C option, in practice.

In the implementation, I would convert it to C and call libsvm
similarly to how scale_C is working now. The reason that I piped up on
the list was purely for code readability. If I read

svm = SVC(C=10)

it really looks like svm is an SVM model with C=10.  If there's a
implicit scale_C=True in the arguments, it's confusing.  This caused
my code to have a bug, and I got annoyed.

On the other hand if I had read

svm = SVC(alpha=1e-3)

then I would have wondered "what's alpha?" and gone to look up the
docs and learn how alpha is converted to C.

- James

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