[GRASS-dev] adding lib_arraystats

[Moritz Lennert]

On 12/02/08 03:43, Dylan Beaudette wrote:
> On Monday 11 February 2008, Moritz Lennert wrote:
>> Hello,
>>
>> I've finally gotten around to continue working on the d.thematic.*
>> modules, and more specifically on the classification code. As mentioned
>> earlier, I think it makes sense to make the latter into a library, so I
>> decided to create lib_arraystats which contains functions for collecting
>> basic statistics and for finding class breaks in arrays of doubles. In
>> the future this could be filled with more statistical functions on such
>> arrays.
>>
>> Could the gurus please have a look and tell me if the attached files are
>> decent enough (except for the lacking documentation) to be committed to
>> svn for further development ? Once that's done, I can also commit the
>> d.thematic.area and v.class modules.
>>
>> Moritz
> 
> Nice work Moritz.
> 
> On this thread-- it would be neat if we can use (along side Moritz's and 
> existinf stat libs) the shared R library, when available. I think that it 
> would have to be a compile-time option, and the user would have to have R 
> installed, and compiled with the '--enable-R-shlib' flag. This would allow us 
> to switch between the default, basic set of algorithms, and the entire suite 
> of R codes. Some of these functions might not work with huge datasets (R 
> works with data in-memory)-- but it would allow us to program more 
> complicated algorithms without re-inventing them.

I agree that having a more direct link to R would be nice. At the same, 
I'm not sure if we should do this across all modules using stats. Maybe 
a g.rstats or v.rstats could be an option ?


> This thread reminded me of doing this, as sometimes it is useful to look 
> for "natural classes" within data. Instead of re-implementing a variation of 
> K-means, we could just pass an array to the appropriate (set of) R functions.
> 

I've done this, but via the plr interface between R and PostgreSQL. See 
attached script for an example.

Moritz
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