[GRASS-dev] reg i.pca module

[Rashad M]

Hi,

I am trying to develop a tool for grass which is one of the things that
xgobi[1] does. The idea is from Markus Neteler which is to identify pure
pixel/end members from a PCA plot. Since i.pca transforms pixel position is
lost. So I need to find out how the pixel values are changed during a PC
Analysis. spectral unmixing (i.spec.unmix) needs pure pixels for
classification which is not easy to obtain or needs a device field
spectrometer which is expensive. So a module in GRASS GIS to do will make
the life a lot easier

[1] http://www2.research.att.com/areas/stat/xgobi/


On Thu, Feb 7, 2013 at 1:16 PM, Nikos Alexandris <nik at nikosalexandris.net>wrote:

> [all deleted]
>
> Hey Rashad,
>
> i.pca will output for you Principal Components.  As many variables you will
> feed to the algorithm (PCA), as many Principal Components you will get.
>
> You don't need, normally, to do anything else than use the Principal
> Components.  I.e., you can selectively reject some Principal Components
> which
> are not of interest and play with the rest.  The simplest example that
> falls
> into my mind is, e.g. to discard the last Pincipal Component which is
> "famous"
> as to hold noise.
>
> Could you please elaborate a bit more on what exactly you are after?  It
> depends on how much detail you want to squeeze out of PCA -- I mean,
> understand each and every step and, possibly, modify the algorithm (?).
>
> Best, Nikos




-- 
Regards,
   Rashad
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