[R-sig-Geo] polygonValues (raster): Very slow

[Pierre Racine]

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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