2012/9/5 Nelle Varoquaux <nelle.varoqu...@gmail.com>
>
>
> On 5 September 2012 09:28, Matthieu Brucher <matthieu.bruc...@gmail.com>wrote:
>
>>
>>
>> 2012/9/5 Nelle Varoquaux <nelle.varoqu...@gmail.com>
>>
>>>
>>>
>>> On 5 September 2012 08:08, Matthieu Brucher
>>> <matthieu.bruc...@gmail.com>wrote:
>>>
>>>> Excellent work!
>>>> I have a question on MDS. Is it the classic MDS or something else?
>>>> (Asking the question as PCA is the classic MDS). It seems to be when the
>>>> distance matrix is Euclidean?
>>>>
>>>
>>> It is indeed the classical MDS. When the whole similarity matrix,
>>> indeed, the classical MDS is equivalent to a PCA. But when there a missing
>>> values, PCA don't work.
>>> An improvement to do to the current implementation is to use the PCA
>>> when the whole matrix is provided. That should speed it up a lot.
>>>
>>> Cheers,
>>> N
>>>
>>
>> Hi Nelle,
>>
>> Thanks for the intel, I forgot it could handle sparse matrices.
>> One additional question: is it possible to have details on the minimized
>> cost function? As there are thousands of different possibilities, sometimes
>> dealing with outiliers (ans so shortcuts), small values...
>>
>
> Sure. I'll add that to the documentation during the code sprint. If I
> remember correctly, I just use the raw stress, but I need to check that.
>
> Cheers,
> N
>
Thanks ;)
Matthieu
--
Information System Engineer, Ph.D.
Blog: http://matt.eifelle.com
LinkedIn: http://www.linkedin.com/in/matthieubrucher
Music band: http://liliejay.com/
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