[postgis-users] ST_Quantile

[Stephen Woodbridge]

Joan,

I've never used these function, but try doing:

select st_quantile('kbd_ext', 'rast', 0.75);

Since you probably do not want this called once for every row in the table.

-Steve

On 1/27/2012 2:03 PM, Joan wrote:
> Hi Bborie,
>
> This is my query and it crashes the db server.
> select st_quantile('kbd_ext', 'rast', 0.75) from kbd_ext limit 10;
>
> Joan
>
> On 27 January 2012 19:14, Bborie Park <bkpark at ucdavis.edu
> <mailto:bkpark at ucdavis.edu>> wrote:
>
>     Hey Joan,
>
>     Assuming your whole coverage is in a table, you should use the
>     table/column version of ST_Quantile (which by the looks of it is
>     undocumented for some reason).
>
>     The function definition of ST_Quantile(rastertable, rastercolumn) is...
>
>     st_quantile(rastertable text, rastercolumn text, nband int DEFAULT
>     1, exclude_nodata_value boolean DEFAULT TRUE, quantiles double
>     precision[] DEFAULT NULL)
>
>     At the moment an aggregate version of ST_Quantile (and the other
>     basic stats functions) does not exist.  It is expected that one will
>     be written for PostGIS 2.1 assuming dev-time is available.
>
>     -bborie
>
>
>     On 01/27/2012 09:06 AM, Joan wrote:
>
>         Hi,
>
>         I would like to find the quantile values of a whole raster
>         coverage, but
>         ST_Quantile returns quantile values of each tile. Which would be
>         the best
>         method to approximate the quantile value of the whole coverage?
>
>         Regards,
>
>         Joan
>
>
>
>
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>     --
>     Bborie Park
>     Programmer
>     Center for Vectorborne Diseases
>     UC Davis
>     530-752-8380
>     bkpark at ucdavis.edu <mailto:bkpark at ucdavis.edu>
>
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