[GRASS-user] r.kappa query

[Markus Metz]

On Fri, Apr 1, 2011 at 2:45 PM, daniel mcinerney
<daniel.o.mcinerney at gmail.com> wrote:
> Hi list,
>
> I have a query regarding the error matrix produced
> using r.kappa (in GRASS 6.4.0 RC6) and hoping that
> the following will help someone to replicate my findings.
> From what I see, the error matrix is mis-labeling the
> rows/columns in the matrix.
>
Right, I noticed that some months ago, but fixed it only in grass 7.
Now also fixed in 6.5 and 6.4 (r45818 and r45819, respectively).

Markus M

> Using the spearfish dataset, I digitised 18 points
> to create a reference dataset to validate
> the classification, in this case the raster 'landcover.orig'
> For the purposes of the test and simplicity, I ensured
> that the points  were located within two landcover classes
> (raster values 42 and 81). The following steps were carried out
> to generate the output from r.kappa
>
>
> #Create reference dataset
> d.where | r.what input=landcover.orig > kappa_test.txt
>
> For the purposes of this test, I deliberately changed the
> landcover class from 42 to 32 in the validation dataset [1]
> This will create an off-diagonal value in the error matrix.
>
> #Create the vector point from ascii and convert to raster
> v.in.ascii input=kappa_test output=kapp_test cat=4
> v.to.rast input=kapp_test output=validation use=cat
>
> #Run r.kappa
> r.kappa classification=landcover.orig reference=validation
> output=validation.txt
>
> The output from r.kappa  (validation.txt) is below, however, it appears
> to me that the matrix is transposed, i.e. the horizontal values
> (MAP1) should in fact be vertical. From my interpretation, the error
> matrix indicates that 8 validation points with the value 42 were
> classified as 32, but in fact it should state that 8 points with
> the value of 32 were classified as 42? Can anyone confirm
> my findings?
>
> Thanks in advance.
>
> Regards,
> Daniel.
>
>
>                         ACCURACY ASSESSMENT
> LOCATION: spearfish60                           Fri Apr  1 12:45:42 2011
> MASK: none
> MAPS: MAP1 = Categories (validation in user1)
>       MAP2 = (untitled) (landcover.orig in PERMANENT)
>
> Error Matrix
> Panel #1 of 1
>                           MAP1
>      cat#       32      42      81      Row Sum
>  M    32        0       8       0       8
>  A    42        0       0       0       0
>  P    81        0       0       10      10
> Col Sum         0       8       10      18
>
>
> Cats    % Commission    % Ommission     Estimated Kappa
> 32      100.000000      -nan    -999.000000
> 42      NA              NA              NA
> 81      0.000000        0.000000        1.000000
>
> Kappa           Kappa Variance
> 0.357143        0.002343
>
> Obs Correct     Total Obs       % Observed Correct
> 10              18              55.555556
>
>
>
> [1]
> #validation input
> 590188.6875|4919453.8125||32
> 590188.6875|4918947||32
> 590307.9375|4918350.75||32
> 590576.25|4917694.875||32
> 590307.9375|4917694.875||32
> 590546.4375|4919364.375||32
> 590874.375|4919364.375||32
> 590904.1875|4919483.625||32
> 603604.3125|4922047.5||81
> 603336|4922315.8125||81
> 603514.875|4922464.875||81
> 603604.3125|4922256.1875||81
> 603634.125|4922107.125||81
> 603693.75|4921987.875||81
> 603962.0625|4921987.875||81
> 603753.375|4921600.3125||81
> 603962.0625|4922047.5||81
> 598983.375|4922256.1875||81
>
>
>
>
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