[postgis-users] ST_SelectByValue

[David Haynes]

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#AccomplishedObjectives>

*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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