[GRASS-user] Fwd: [GRASS-web] r.kappa help

[Markus Neteler]

On Thu, Feb 23, 2017 at 10:42 AM, Moritz Lennert
<mlennert at club.worldonline.be> wrote:
...
> The 'Estimated kappa value' in r.kappa is the value only for one class, i.e.
> the observed agreement between the classifications for those observations
> that have been classified by classifier 1 into the class i. In other words,
> here the choice of reference is important.
>
> It is calculated as (taken from the code [1]):
>
> kpp[i] = (pii[i] - pi[i] * pj[i]) / (pi[i] - pi[i] * pj[i]);
>
> where=
>
> pii[i] is the probability of agreeement (i.e. number of pixels for which
> there is agreement divided by total number of assessed pixels)
> Pi[i] is the probability of classification i having classified the point as
> i
> Pj[i] is the probability of classification j having classified the point as
> i
>
> Hope this helps.
>
> Moritz
>
> [1]
> https://trac.osgeo.org/grass/browser/grass/branches/releasebranch_7_2/raster/r.kappa/calc_kappa.c

I've added that to the manual in trunk (r70667) and relbranch72
(r70668) for the future 7.2.1 version.

Markus

-- 
Markus Neteler
http://www.mundialis.de - free data with free software
http://grass.osgeo.org
http://courses.neteler.org/blog