[postgis-users] ST_Quantile
Bborie Park
bkpark at ucdavis.edu
Fri Jan 27 11:52:58 PST 2012
The way you called ST_Quantile is perfectly acceptable as there are
variants of ST_Quantile that support that form.
I'm fixing the problem now and should have it committed later today.
-bborie
On 01/27/2012 11:42 AM, Joan wrote:
> The 0.75 is the quantile.
>
> I will report the bugs. Thanks for the help/info.
>
> Joan
>
> On 27 January 2012 20:31, Stephen Woodbridge<woodbri at swoodbridge.com>wrote:
>
>> Joan,
>>
>> Looking at the function the Bborie posted:
>>
>>
>> st_quantile(rastertable text, rastercolumn text, nband int DEFAULT
>> 1, exclude_nodata_value boolean DEFAULT TRUE, quantiles double
>> precision[] DEFAULT NULL)
>>
>> The 3rd parameter is the band number. What is the 0.75 supposed to
>> represent? My guess is that is getting truncated to 0 and it is trying to
>> process band=0 which might not be valid.
>>
>> But it should not crash, so please write two bugs against this:
>> 1. for the missing doc
>> 2. for the crash if you enter 0.75
>>
>> Thanks,
>> -Steve
>>
>>
>> On 1/27/2012 2:19 PM, Joan wrote:
>>
>>> Hi Steve,
>>>
>>> I have gotten the same problem (db server stopped running).
>>>
>>> Joan
>>>
>>> On 27 January 2012 20:05, Stephen Woodbridge<woodbri at swoodbridge.com
>>> <mailto:woodbri at swoodbridge.**com<woodbri at swoodbridge.com>>> wrote:
>>>
>>> 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>
>>> <mailto: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
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>>> <mailto:bkpark at ucdavis.edu<mailto:bkpark at ucdavis.edu>>
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--
Bborie Park
Programmer
Center for Vectorborne Diseases
UC Davis
530-752-8380
bkpark at ucdavis.edu
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