On Fri, Jun 21, 2013 at 3:17 PM, Joel Nothman
<jnoth...@student.usyd.edu.au>wrote:
> On Fri, Jun 21, 2013 at 3:07 PM, Mathieu Blondel <math...@mblondel.org>wrote:
>
>>
>> In my research, I have used CSR matrices, since they can be processed
>> very efficiently in Cython. Since CSR matrices are indeed non-trivial to
>> construct, we could provide an utility function which takes an iterator of
>> (feature_index, feature_value) pairs and produces a CSR matrix (with
>> hardcoded zero-values safely preserved).
>> <https://lists.sourceforge.net/lists/listinfo/scikit-learn-general>
>
>
> So are you proposing that sparse matrices encode missing values with nan?
> Or something else?
>
Sorry, I didn't at first appreciate your "hard coded zero-values
preserved". This is fine as long as no one tries to convert it to another
sparse type! So basically, we'll be relying on an implementation detail,
but perhaps that's necessary for efficient sparse-matrix use.
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