Message-ID: <87A96661E65C5541AB4D20721C2DD7F880A316873F@EXCH-MBX-A.ulaval.ca>
Date: 2010-06-30T20:14:22Z
From: Pierre Racine
Subject: polygonValues (raster): Very slow
In-Reply-To: <AANLkTikPNOMFUdF87TsWUcJCoqXX-Am7G5eeMXHDinPf@mail.gmail.com>
Agustin,
PostGIS WKT Raster was made to do exactly this kind of operation on large datasets. Give it a try!
http://trac.osgeo.org/postgis/wiki/WKTRasterTutorial01
Pierre
>-----Original Message-----
>From: r-sig-geo-bounces at stat.math.ethz.ch [mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf Of
>Agustin Lobo
>Sent: 30 juin 2010 10:13
>To: r-sig-geo
>Cc: agustin.lobo at ija.csic.es
>Subject: [R-sig-Geo] polygonValues (raster): Very slow
>
>Hi!
>I'm trying:
>
>> eugrd025EFDC <- readOGR(dsn="eugrd025EFDC",layer="eugrd025EFDC")
>v <- polygonValues(p=eugrd025EFDC, Br, weights=TRUE)
>
>where
>
>> str(eugrd025EFDC,max.level=2)
>Formal class 'SpatialPolygonsDataFrame' [package "sp"] with 5 slots
> ..@ data :'data.frame': 18000 obs. of 5 variables:
> ..@ polygons :List of 18000
> .. .. [list output truncated]
> ..@ plotOrder : int [1:18000] 17901 17900 17902 17903 17899 17898
>17904 17897 17905 17906 ...
> ..@ bbox : num [1:2, 1:2] 2484331 1314148 6575852 4328780
> .. ..- attr(*, "dimnames")=List of 2
> ..@ proj4string:Formal class 'CRS' [package "sp"] with 1 slots
>
>> summary(Br)
>Cells: 13967442
>NAs : 0
>
>
>Min. 0.00
>1st Qu. 0.00
>Median 0.00
>Mean 48.82
>3rd Qu. 0.00
>Max. 4999.00
>
>so quite large objects.
>
>The problem is that polygonValues() has been running (and not
>completed the task) for
>more than 2 h on a intel core i7 machine with 16 Gb RAM (Dell
>Precision M6500), so a pretty powerful machine.
>Is there any way I could speed up this process?
>Also, is there anything I could do in order to take better advantage
>of the 8 processing threads?
>Currently, I see only 1 cpu working for R processes and the rest
>remain pretty inactive
>
>Thanks
>
>Agus
>
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