<div>Hi Bborie,<br></div><div><br></div><div>I have used ST_MapAlgebraExpr but I get the error below. </div><div><br></div><div>
<p class="MsoNormal"><span lang="DE" style="font-size:10.0pt;mso-bidi-font-size:
11.0pt;line-height:115%;font-family:"Courier New"">select * from (select ST_MapAlgebraExpr(kb.rast, kb1.rast, 'kb1.rast+kb.rast') as rast from kb_dsm_clip kb, kb_dsm_clip100 kb1) as r1 limit 5;<br>ERROR: missing FROM-clause entry for table "kb1"<br>
LINE 1: SELECT (KB1.RAST+KB.RAST)::double precision<br> ^<br>QUERY: SELECT (KB1.RAST+KB.RAST)::double precision</span></p>
<p class="MsoNormal"><span lang="DE" style="font-size:10.0pt;mso-bidi-font-size:
11.0pt;line-height:115%;font-family:"Courier New""><span style="mso-spacerun:yes">
</span>^</span></p></div><div><span lang="DE" style="font-size:10.0pt;mso-bidi-font-size:
11.0pt;line-height:115%;font-family:"Courier New""><br></span></div><div><span lang="DE" style="font-size:10.0pt;mso-bidi-font-size:
11.0pt;line-height:115%;font-family:"Courier New""><font face="arial,helvetica,sans-serif">At what point should I add :: double precision, I added it like this and also got an error.</font><font face="arial,helvetica,sans-serif"><br>
</font></span></div><div><span lang="DE" style="font-size:10.0pt;mso-bidi-font-size:
11.0pt;line-height:115%;font-family:"Courier New""><font face="arial,helvetica,sans-serif"><br></font></span></div><div><span lang="DE" style="font-size:10.0pt;mso-bidi-font-size:
11.0pt;line-height:115%;font-family:"Courier New"">select * from (select ST_MapAlgebraExpr(kb.rast, kb1.rast, 'kb1.rast+kb.rast')::double precision as rast from kb_dsm_clip kb, kb_dsm_clip100 kb1) as r1 limit 5;<br>
ERROR: cannot cast type raster to double precision<br>LINE 1: ...AlgebraExpr(kb.rast, kb1.rast, 'kb1.rast+kb.rast')::double p...<br> ^<br></span></div><div>
<br></div><div>Regards </div><div><br></div><div>Joan<br></div><div><br></div><div><br></div><div class="gmail_quote">On 21 November 2011 16:06, Bborie Park <span dir="ltr"><<a href="mailto:bkpark@ucdavis.edu" target="_blank">bkpark@ucdavis.edu</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div>On Mon, Nov 21, 2011 at 7:02 AM, Joan <<a href="mailto:wamaithajoan@gmail.com" target="_blank">wamaithajoan@gmail.com</a>> wrote:<br>
> Hello,<br>
><br>
> When I run the following query<br>
> select ST_MapAlgebra(r1.rast, r2.rast, "rast1 + rast2") from (select<br>
> r1.rast, r2.rast from r1, r2) as foo limit 10;<br>
> I get this error<br>
> ERROR: column "rast + rast" does not exist<br>
> LINE 1: ...t * from (select ST_MapAlgebra(r1.rast, r2.rast, "rast + ra...<br>
> ^<br>
> What could be the problem? What is the correct syntax for st_mapalgebra?<br>
> I have PostGIS installed the version updated on 18th Nov 2011.<br>
><br>
> Joan<br>
<br>
</div></div>Hey Joan,<br>
<br>
You'll want to use ST_MapAlgebraExpr or ST_MapAlgebraFct.<br>
<br>
<a href="http://postgis.refractions.net/documentation/manual-svn/RT_reference.html#Raster_Processing" target="_blank">http://postgis.refractions.net/documentation/manual-svn/RT_reference.html#Raster_Processing</a><br>
<span><font color="#888888"><br>
-bborie<br>
<br>
--<br>
Bborie Park<br>
Programmer<br>
Center for Vectorborne Diseases<br>
UC Davis<br>
530-752-8380<br>
<a href="mailto:bkpark@ucdavis.edu" target="_blank">bkpark@ucdavis.edu</a><br>
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</font></span></blockquote></div><br>