[postgis-users] raster, stats conditioned to a set of values

[juli g. pausas]

Thanks for this.
But it didn't work for me.

These queries work

SELECT (ST_SummaryStats(ST_MapAlgebra(rast, 1, '16BSI'::text, '[rast]+1'),
1)).* FROM rastertmp.ndvitmp
SELECT (ST_SummaryStats(ST_MapAlgebra(rast, 1, NULL, '[rast]+1'), 1)).*
FROM rastertmp.ndvitmp

But not when I use the condition [rast] > 0

SELECT (ST_SummaryStats(ST_MapAlgebra(rast, 1, NULL, '[rast] > 0'), 1)).*
FROM rastertmp.ndvitmp

ERROR:  cannot cast type boolean to double precision
LINE 1: SELECT ($1 > 0)::double precision

Replacing NULL for '16BSI'::text, or '16BSI'::smallint, '16BSI'::double
precision doen't solve the problem

Any other suggestion?
Thanks






Juli
--
*CIDE, CSIC*  |  www.uv.es/jgpausas  |


On Tue, Jun 30, 2015 at 5:29 PM, Pierre Racine <Pierre.Racine at sbf.ulaval.ca>
wrote:

> You can select pixels fulfilling an expression using the one-raster
> variant of ST_MapAlgebra
>
> http://postgis.net/docs/RT_ST_MapAlgebra_expr.html
>
> So just do something like:
>
> ST_MapAlgebra(rast, '8BUI'::text, '[rast] > 0')
>
> before computing stats.
>
> To count the number of pixels of a certain value you can use
> ST_ValueCount().
>
> Pierre
>
> > -----Original Message-----
> > From: postgis-users-bounces at lists.osgeo.org [mailto:postgis-users-
> > bounces at lists.osgeo.org] On Behalf Of juli g. pausas
> > Sent: Monday, June 29, 2015 12:49 PM
> > To: PostGIS Users Discussion
> > Subject: [postgis-users] raster, stats conditioned to a set of values
> >
> > Hi all
> >
> > I'm just starting to discover postgis, it is really useful.
> >
> > I have a raster file with different bands, that I have imported to
> postgres
> > (raster2pgsql, without the -R option, i.e., insite the database). I
> would like to
> > extract information from band 1, but filtering the data using only
> >
> > 1) pixels with positive values (in that band, band 1)
> >
> > 2) and pixels in which band 2 is equal to a given value, e.g. 1
> >
> >
> > The type of analysis I'd like to do is descriptive stats but also
> intersecting
> > with a vector map. If my raster is rastertmp.ndvitmp, two examples are:
> >
> >
> > SELECT (ST_SummaryStats(rast, 1)).* FROM rastertmp.ndvitmp WHERE rid
> > = 1
> >
> >
> >
> > SELECT p.region_cod, ST_ValueCount(ST_Clip(r.rast,1, p.geom, true)) AS
> res
> >   FROM gis_wd.wd_regiones AS p, rastertmp.ndvitmp AS r
> >   WHERE ST_Intersects(r.rast, p.geom)
> >   AND p.region_cod = 'PA1214';
> >
> >
> >
> > This works perfectly, but how can I compute the stats  only for pixels
> with
> > positive values and with a given value in another band?  The idea would
> be
> > something like:  WHERE ST_Values(rast, 1)>0 AND ST_Values(rast, 2)=1
> >
> >
> > Thanks for any help!
> >
> >
> > Juli
> > --
> > CIDE, CSIC  |  www.uv.es/jgpausas  |
> >
>
> _______________________________________________
> postgis-users mailing list
> postgis-users at lists.osgeo.org
> http://lists.osgeo.org/cgi-bin/mailman/listinfo/postgis-users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20150701/2ef81737/attachment.html>