[GRASS-dev] [GRASS GIS] #3296: r.mapcalc: nmedian() unexpected results

[GRASS GIS]

#3296: r.mapcalc: nmedian() unexpected results
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 Reporter:  sbl                  |      Owner:  grass-dev@…
     Type:  defect               |     Status:  new
 Priority:  normal               |  Milestone:  7.2.1
Component:  Default              |    Version:  svn-releasebranch72
 Keywords:  r.mapcalc,nmedian()  |        CPU:  Unspecified
 Platform:  Unspecified          |
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 Seems that the nmedian() function in r.mapcalc for both GRASS 7.0,  GRASS
 7.2 and trunk gives unexpected results.
 The neighborhood modifer I used do not seem to cause the issue...

 This:
 {{{
 g.region -p n=3 s=0 e=3 w=0 res=1
 r.mapcalc expression="test=row()*col()" --o
 r.mapcalc expression="nbh_test_r=(test[0,-1] - test)^2.0" --o
 r.mapcalc expression="nbh_test_l=(test[0,1] - test)^2.0" --o
 r.mapcalc expression="nmed_test=nmedian(((test[0,-1] -
 test)^2.0,(test[0,1] - test)^2.0))" --o
 }}}
 should result in a horizontally striped map with values covering 1 (top
 row), 4 (middle row, and 9 (bottom row). However, the leftmost column
 contains values 0.2, 2.5, 6.5 (from top to bottom).

 Yet, here - where values only differ from column to column -
 {{{
 r.mapcalc expression="test=col()" --o
 r.mapcalc expression="nmed_test=nmedian(((test[0,-1] -
 test)^2.0,(test[0,1] - test)^2.0))" --o
 }}}
 only the top-left cell has an odd value of 0.5 while the rest has value 1
 as expected...

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Ticket URL: <https://trac.osgeo.org/grass/ticket/3296>
GRASS GIS <https://grass.osgeo.org>