#1668: r.regression.line F-test incorrect
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Reporter: cmbarton | Owner: grass-dev@…
Type: defect | Status: new
Priority: normal | Milestone: 7.0.0
Component: Raster | Version: unspecified
Keywords: | Platform: Unspecified
Cpu: Unspecified |
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Comment(by mlennert):
Replying to [comment:4 mmetz]:
> You can compare to the grass7 addon r.regression.multi whose results are
identical to those of R.
This is what I did and actually r.regression.line with the above change
gives the same result as R, not r.regression.multi (regressing the landsat
bands 10 and 20 from the NC data set):
F (R): 6268922
F (r.regression.line with change): 6268922.212939
F (r.regression.multi): 6268947.256273
I think I've found the problem in r.regression.multi:
Instead of
{{{
F = ((SStot - SSerr) * (count - n_predictors)) / (SSerr * n_predictors);
}}}
it should be
{{{
F = ((SStot - SSerr) * (count - n_predictors - 1)) / (SSerr *
n_predictors);
}}}
Moritz
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Ticket URL: <http://trac.osgeo.org/grass/ticket/1668#comment:5>
GRASS GIS <http://grass.osgeo.org>
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