[GRASS-user] What output from r.topidx?

[Markus Metz]

Rich Shepard wrote:
>   Following the example on the r.topidx man page I ran the two following
> commands:
first, make sure the region is set properly with
g.region rast=aberDEM -p

if cells in house_catchment outside the catchment of interest are NULL, 
you can do

g.region zoom=house_catchment
g.region align=aberDEM

to reduce the region and thus computational time and memory requirements 
before running r.mapcalc and r.topidx
>
> r.mapcalc "house_elev = if (isnull(aberDEM), aberDEM, house_catchment)"
doesn't make sense to me, and does not correspond to the example in the 
man page. try
r.mapcalc "house_elev = if (isnull(house_catchment), null(), aberDEM)"

you need some elevation map as input for r.topidx, house_elev will now 
be a masked raster elevation map, if cells in house_catchment outside 
the catchment of interest are NULL. if they are e.g. zero, the command 
would be
r.mapcalc "house_elev = if (house_catchment == 0, null(), aberDEM)"

if cells in house_catchment outside the catchment of interest are NULL, 
you could also
g.copy rast=house_catchment,MASK

or if cells in house_catchment outside the catchment of interest are 
something else than NULL, you could do
r.mapcalc "MASK = if(house_catchment == <my_mask_value>, null(), 1)"

and now run r.topidx

obviously all this only works if aberDEM covers at least some parts of 
the catchment of interest in house_catchment

>
> r.topidx in=house_elev out=house_tci
>
>   I can find no output. house_tci does not display in a monitor, running
> r.stats -Anc house_tci out=house_stats
> produced an empty file, and so did
> r.reports house_tci
>
>   What have I missed here that I find no output at tall?
>
> Rich
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