Giovanni, thank you for your proposal.
The link to the FAQ (the one that Jose provided) looks like a solution. But your idea is clever as well and I had a similar way in my mind. If I got it correct you suggest: 1. VectorTargetAreas ~~~v.to.rast (based on unique attribute like cat or FID~~~> RasterTargetAreas (all pixels of a "TargetArea" have now the same value 2.MASK out everything besides the "TargetAreas" ---looping to create as many MASKS as the the number of the "TargetAreas" 3. For each MASK run r.stats 4 (I would also like to have) add the output list(s) as a new table (column pixval) into the initial VectorTargetAreas (with db.connect, db.addcol, etc). Let's say for a polygons which covers 20 pixels it would be like: FID - cat - pixval 1 - 1 - 200 2 - 1 - 198 3 - 1 - 234 .. - .. - ..... 20 - 1 - 765 Is it possible to put all this together? r.stats and output into a new column (pixval) On Thu, 2008-01-17 at 18:25 +0100, G. Allegri wrote: > Just a rapid idea. > You could make just one rasterized map of your polygons and then > insert in a loop this, giving each pixel a unique category value: > > r.mapcalc "MASK = if(raster=$i,1,null())" > with $1 the cat value (deriving from you original polygon) > > and then run r.stats, which will work only for the un-masked pixels. > > I don't have time to try this method, hope it helps. > GIovanni > > 2008/1/17, [EMAIL PROTECTED] > <[EMAIL PROTECTED]>: > > Salut Jose! > > > > This is what I am doing... and I only have 7 polygons - so > > it is ok. > > > > But if I have 50 polygons... I am not so sure how to script > > it to get (finally) a table with all pixels for each unique > > polygon for 2 different images of the same location (for > > raster MODIS year 2006 and then another of the same area > > MODIS 2007!). > > > > I want to run a regression with the pixel values... (pairs > > of 2006 and 2007 values). > > > > Thank you, > > > > Nikos. > > > > > > > > On Thu, 17 Jan 2008 16:42:31 +0000 > > "Jose Gomez-Dans" <[EMAIL PROTECTED]> wrote: > > > On Jan 17, 2008 4:30 PM, > > > <[EMAIL PROTECTED]> wrote: > > > > > > > How can I get listed all unique pixel values enclosed > > > in > > > > each of the polygons I digitised (and for which the > > > univ. > > > > stats are calculated)? > > > > > > > > > > Can't you just rasterise your polygons, and use that as a > > > mask with > > > r.mapcalc? You can loop around in your shell. I tend to > > > do that with python, > > > but it's similar in GRASS. You can also try starspan. > > > Or.... < > > > http://grass.gdf-hannover.de/wiki/Aggregate_Values> > > > > > > Cheers, > > > Jose > > > > > > > > > > > > -- > > > Centre for Terrestrial Carbon Dynamics > > > Department of Geography, University College London > > > Gower Street, London WC1E 6BT, UK > > > > > > . > > Nikos Alexandris - Ph.D. Candidate > > . > > Department of Remote Sensing > > and > > Landscape Information Systems > > (FeLIS) > > . > > Faculty of Forestry and Natural Environment > > Albert-Ludwigs-University Freiburg > > . > > Tel. +49 (0) 761 203 3697 > > Fax. +49 (0) 761 203 3701 > > Skype: Nikos.Alexandris > > . > > Address: Tennenbacher str. 4 > > D-79106 Freiburg i. Br. > > Germany > > . > > _______________________________________________ > > grass-user mailing list > > grass-user@lists.osgeo.org > > http://lists.osgeo.org/mailman/listinfo/grass-user > > -- Nikos Alexandris . Department of Remote Sensing & Landscape Information Systems Faculty of Forestry & Environmental Sciences, Albert-Ludwigs-University Freiburg . Tel. +49 (0) 761 203 3697 / Fax. +49 (0) 761 203 3701 / Skype: Nikos.Alexandris . Address: Tennenbacher str. 4, D-79106 Freiburg i. Br., Germany
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