Try ST_Reclass(). > -----Original Message----- > From: [email protected] [mailto:postgis-users- > [email protected]] On Behalf Of David Haynes > Sent: Friday, May 30, 2014 10:49 AM > To: [email protected] > Subject: [postgis-users] ST_SelectByValue > > Hello, > > I am fairly new to using rasters in postgis, but I am wondering if there is a > faster way to extract values from categorical rasters (e.g. landcover types) > than using map algebra. In the PostGIS in Action book, pg 404 has a > function called ST_SelectByValue(raster|geometry, 'expression') which > seems to incorporate map algebra, however I can't seem to tell if this > function is finished and available in postgis as I get an unknown function > error. > > My version is this. > "PostgreSQL 9.3.2 on x86_64-unknown-linux-gnu, compiled by gcc > (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3, 64-bit POSTGIS="2.1.1 r12113" > GEOS="3.3.3-CAPI-1.7.4" PROJ="Rel. 4.7.1, 23 September 2009" > GDAL="GDAL 1.9.0, released 2011/12/29" LIBXML="2.7.8" LIBJSON="UN > (...)" > > > And I found a webpage > http://trac.osgeo.org/postgis/wiki/WKTRaster/SpecificationWorking03 > > search for "ST_SelectByValue" at the bottom, indicating that it was finished. > > > AAccomplished Objectives > <http://trac.osgeo.org/postgis/wiki/WKTRaster/SpecificationWorking03#A > ccomplishedObjectives> > > > ST_ValueCount(raster, value) -> integer - done see below > > ST_ValuePercent(raster, value) -> double precision - done see below > > ST_Resample(raster, method, originx, originy, pixelsizex, pixelsizey) -> > raster > - done see below > > ST_SelectByValue(raster, 'expression') -> same type as first argument > > ST_Clip(raster|geometry,geometry) -> same type as first argument
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