[Qgis-user] Extract raster cell-value statistics (min, max, count, sum) within a polygone

[Johan Nilsson]

Thanx Micha Silver :)
Worked now after setting region S and W and also change resolution to what
the raster had. :)



2015-04-29 18:44 GMT+02:00 Micha Silver <micha at arava.co.il>:

>
>
> On 04/29/2015 03:15 PM, Johan Nilsson wrote:
>
>  Have now tried to run v.rast.stats in Grass 7.0. It start and run 100%
> off one core in hours, until a file in ~/grassdata/location/PERMANENT/.tmp/
> inflate to the disk is full, approximate 150GB :(
>
>   Whoa!
> Check the region settings before you try again:
> g.region -p
> This is FAQ #0 for all work with GRASS. The v.rast.stats module works by
> first rasterizing the vector polygons into a temporary raster. If you
> region is very large, and resolution setting is very small, you might be
> getting a huge temporary raster.
>
>
>  Have made topology check on the vector-data and imported it to grassdb.
> Will see if I can collect usefull data and ask on grass-user list.
>
>  Stupid Ubuntu 14.04  to not messure invisible files in the normal
> file-manager, had gone faster to pinpoint the problem.
>
>  /Cheers
>
> 2015-04-19 18:54 GMT+02:00 Micha Silver <micha at arava.co.il>:
>
>>
>>
>> On 04/19/2015 12:34 PM, Johan Nilsson wrote:
>>
>>  Zonal statistics work well to extract, numers of cells(counts) , sum of
>> the value (sum)  and also average (mean) But I want the minimum AND
>> max-value and also standard error, if possible. Is there another plugin or
>> a tutorial how it may bee done in another way.
>>
>>    The GRASS module v.rast.stats does what you want. But it's not in the
>> Processing toolbox. You can import your raster into a GRASS mapset then do
>> the analysis directly within GRASS.
>>
>>  The code to Zonal statistics are here, but I'm total lost in how it
>> work.
>>
>>
>> https://github.com/qgis/QGIS/blob/a2f51260db5357917e86b78f1bb2915379d670dd/src/analysis/vector/qgszonalstatistics.cpp
>>
>>  /Cheers
>>
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