[Qgis-developer] R: help for processing algorithms

[Iacopo Borsi]

Hi,
it seems that my problem was in the GRASS algorithm I was using. Now, I've moved to GDAL algorithm named "Grid - InverseDistance To a Power" and it works. Really, I don't know what was wrong: my only suspect is that after running grass algorithm I would need to "convert" the grass raster map created to a "readble" raster, to be loaded in QGis correctly. I realized such a guess after reading the processing log file and comparing the log obtained by python-based run with the one obtained after launching the process by the GUI. But this is only a guess... hoping this could help somebody else playing with GRASS and processing.

Iacopo 

-----Messaggio originale-----
Da: Victor Olaya [mailto:volayaf at gmail.com] 
Inviato: martedì 21 luglio 2015 15:34
A: Iacopo Borsi <iacopo.borsi at tea-group.com>
Cc: qgis-developer at lists.osgeo.org
Oggetto: Re: [Qgis-developer] help for processing algorithms

Iacopo

What do you mean by "it fails"? do you see any error? or it just doesn't add any layer to your QGIS project?

You have to use Processing.runandload if you want that. Otherwise, the runalg method returns a dictionary in which keys are output names, and values are ouput paths where your outputs have been generated, and you have to load them manually into QGIS

Hope this helps




2015-07-21 14:57 GMT+02:00 Iacopo Borsi <iacopo.borsi at tea-group.com>:
> Hi,
>
> I’m new to this list, so I don’t know if this is the right place to 
> post my issue…. Sorry for that.
>
>
>
> However, my problem is about running processing algorithm directly 
> from a python script.
>
> I’m using QGis 2.8 under Windows 7, and python correctly installed 
> under Qgis directory.
>
>
>
> This is the problem: if I run a GRASS algorithm using the GUI, 
> everything is ok.
>
> The same algorithm, with the same source input file and applying the 
> same parameters… it fails when called by processing through a (very 
> simple!) Python script.
>
>
>
> Now, after several tests, I’m also using the point shape file embedded 
> under processing/test folder (just to be sure of integrity of input file).
>
> If you see below, I’m also looking at processing.log, and what is 
> surprising is that logs seem exactly the same !!!
>
>
>
> I post below the short code I’m using and the log file I got.
>
> Again, I remark that the algorithm run from GUI is perfectly working 
> :-0
>
>
>
> Any help or suggestion?
>
>
>
> Thank you so much in advance.
>
> Iacopo
>
>
>
> My python code to run Inverse Distance Squared Weighting interpolator 
> (GRASS).
>
>
>
> ---
>
> from PyQt4.QtGui import *
>
> from qgis.core import *
>
> from qgis.gui import *
>
> from PyQt4.QtCore import *
>
> import processing
>
>
>
> # Define the data source
>
> vl = iface.activeLayer()
>
> if vl.isValid() :
>
>     print 'Layer is valid!'
>
>
>
> # Extent
>
> ext = vl.extent()
>
> xmin = ext.xMinimum()
>
> ymin = ext.yMinimum()
>
> xmax = ext.xMaximum()
>
> ymax = ext.yMaximum()
>
>
>
> # Name of the field
>
> myfield = 'PT_NUM_A'
>
>
>
> # Run Grass alg
>
> out_ras = processing.runalg("grass:v.surf.idw", vl , 12 ,2.0, myfield ,
> False,   "%f , %f, %f, %f "% (xmin , xmax , ymin , ymax), 10.0, -1, 0.001,
> None)
>
>
>
> # retrieve the raster output and load it in Qgis:
>
> fileoutput= out_ras['output']
>
> fileInfo = QFileInfo(fileoutput)
>
> baseName = fileInfo.baseName()
>
> rlayer = QgsRasterLayer(fileoutput, baseName)
>
> if rlayer.isValid():
>
>     QgsMapLayerRegistry.instance().addMapLayer( rlayer )
>
> else:
>
>      print 'Raster layer is not valid!'
>
>
>
> ****
>
> Log info I got from processing.log
>
> ---
>
> Using GUI:
>
> ---
>
> ALGORITHM|Tue Jul 21 2015
> 14:39:01|processing.runalg("grass:v.surf.idw","C:\\Users\\iacopo.borsi
> \\.qgis2\\python\\plugins\\processing\\tests\\data\\points.shp",12,2,"
> PT_NUM_A",False,"270778.60198,270855.745301,4458921.97814,4458983.8488
> ",10,-1,0.0001,None)
>
> INFO|Tue Jul 21 2015 14:39:01|GRASS execution commands|g.proj -c
> proj4="+proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 
> +units=m
> +no_defs"|v.in.ogr min_area=0.0001 snap=-1
> dsn="C:\Users\iacopo.borsi\.qgis2\python\plugins\processing\tests\data"
> layer=points output=tmp14374823414715 --overwrite -o|g.region 
> n=4458983.8488
> s=4458921.97814 e=270855.745301 w=270778.60198 res=10|v.surf.idw
> input=tmp14374823414715 npoints="12" power="2" column="PT_NUM_A"
> output=outputbcda77408a344d7a98a6046195dfd47f --overwrite|g.region 
> rast=outputbcda77408a344d7a98a6046195dfd47f|r.out.gdal -c 
> createopt="TFW=YES,COMPRESS=LZW"
> input=outputbcda77408a344d7a98a6046195dfd47f
> output="C:\Users\IACOPO~1.BOR\AppData\Local\Temp\processing\03d92082eed7415b98b492b4eed62250\output.tif"
>
>
>
> ---
>
> Using my script, launched by Python Console within QGis:
>
> ---
>
> ALGORITHM|Tue Jul 21 2015
> 14:39:44|processing.runalg("grass:v.surf.idw","C:\\Users\\iacopo.borsi
> \\.qgis2\\python\\plugins\\processing\\tests\\data\\points.shp",12,2,"
> PT_NUM_A",False,"270778.601980 , 270855.745301, 4458921.978139, 
> 4458983.848803 ",10,-1,0.0001,None)
>
> INFO|Tue Jul 21 2015 14:39:44|GRASS execution commands|g.proj -c
> proj4="+proj=utm +zone=30 +ellps=intl +towgs84=-87,-98,-121,0,0,0,0 
> +units=m
> +no_defs"|v.in.ogr min_area=0.001 snap=-1
> dsn="C:\Users\iacopo.borsi\.qgis2\python\plugins\processing\tests\data"
> layer=points output=tmp14374823847716 --overwrite -o|g.region n=
> 4458983.848803  s= 4458921.978139 e= 270855.745301 w=270778.601980 
> res=10|v.surf.idw input=tmp14374823847716 npoints="12" power="2"
> column="PT_NUM_A" output=output86e01c9844a44af89394d73b4f384b5e
> --overwrite|g.region 
> --overwrite|rast=output86e01c9844a44af89394d73b4f384b5e|r.out.gdal
> -c createopt="TFW=YES,COMPRESS=LZW"
> input=output86e01c9844a44af89394d73b4f384b5e
> output="C:\Users\IACOPO~1.BOR\AppData\Local\Temp\processing\96562ff5412640439c7dd19dffe60ac0\output.tif"
>
>
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