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    Joan,<br>
    <br>
    I think your expression is wrong.<br>
    <span style="font-size:10.0pt;mso-bidi-font-size:
      11.0pt;line-height:115%;font-family:"Courier New""
      lang="DE">'kb1.rast+kb.rast'</span> <br>
    should be: <br>
    'rast1+rast2'<br>
    <br>
    Oddly enough, I would not expect this error message with that error,
    so I'm curious wether it will make a change. Could it be there is
    any more quotes in the query that we can't see?<br>
    <br>
    Chrs,<br>
     Tom<br>
    <br>
    On 22-11-2011 14:24, Joan wrote:
    <blockquote
cite="mid:CAAjRq6jrPdircd5YxvYB3vvEepDd9dR18_sOkp2CpNxR7xb=wA@mail.gmail.com"
      type="cite">
      <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
            style="font-size:10.0pt;mso-bidi-font-size:
            11.0pt;line-height:115%;font-family:"Courier New""
            lang="DE">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
            style="font-size:10.0pt;mso-bidi-font-size:
            11.0pt;line-height:115%;font-family:"Courier New""
            lang="DE"><span style="mso-spacerun:yes">                                                            
            </span>^</span></p>
      </div>
      <div><span style="font-size:10.0pt;mso-bidi-font-size:
          11.0pt;line-height:115%;font-family:"Courier New""
          lang="DE"><br>
        </span></div>
      <div><span style="font-size:10.0pt;mso-bidi-font-size:
          11.0pt;line-height:115%;font-family:"Courier New""
          lang="DE"><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 style="font-size:10.0pt;mso-bidi-font-size:
          11.0pt;line-height:115%;font-family:"Courier New""
          lang="DE"><font face="arial,helvetica,sans-serif"><br>
          </font></span></div>
      <div><span style="font-size:10.0pt;mso-bidi-font-size:
          11.0pt;line-height:115%;font-family:"Courier New""
          lang="DE">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 moz-do-not-send="true"
            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
                moz-do-not-send="true"
                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 moz-do-not-send="true"
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 moz-do-not-send="true" href="mailto:bkpark@ucdavis.edu"
                target="_blank">bkpark@ucdavis.edu</a><br>
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