[GRASS-dev] [GRASS GIS] #2969: r.series: wrong usage of weights

[GRASS GIS]

#2969: r.series: wrong usage of weights
-------------------------------+-------------------------
 Reporter:  mmetz              |      Owner:  grass-dev@…
     Type:  defect             |     Status:  new
 Priority:  normal             |  Milestone:  7.0.4
Component:  Raster             |    Version:  7.0.3
 Keywords:  r.series, weights  |        CPU:  Unspecified
 Platform:  All                |
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 A weighted average is calculated with

 {{{
 avg = sum(w[i] * x[i]) / sum(w[i])
 }}}

 r.series calculates weighted averages with
 {{{
 avg = sum(w[i] * x[i]) / count
 }}}

 r.series should instead behave like r.neighbors and use the corresponding
 weighing functions from libstats if available.

 Test commands:
 {{{
 # set the region
 g.region -p n=10 s=0 w=0 e=10 res=1
 # create identical input maps
 r.mapcalc "input1 = 1"
 r.mapcalc "input2 = 1"
 r.mapcalc "input3 = 1"
 r.mapcalc "input4 = 1"
 r.mapcalc "input5 = 1"

 # average
 r.series in=input1,input2,input3,input4,input5 method=average out=avg
 # weighted average
 r.series in=input1,input2,input3,input4,input5 method=average out=avg_w
 weights=0.1,0.2,0.3,0.2,0.1
 }}}

 Without weights the result is 1, with weights the result is 0.18 instead
 of 1. Weights have been added to r.series in r49946. I am going to change
 r.series in trunk and relbr70.

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Ticket URL: <https://trac.osgeo.org/grass/ticket/2969>
GRASS GIS <https://grass.osgeo.org>