[postgis-users] monthly climate query
Kirk Wythers
kwythers at umn.edu
Wed Aug 15 11:58:19 PDT 2007
You were right Regina. I did some testing and the subselects were
indeed returning averages for the entire weather table.
I also pulled all the -999 values out and replaced them with NULLs.
The way it should have been in the first place.
Here is my latest crack at your suggestions (including getting rid of
the double subselect), However I'm getting syntax error at the FROM
weather line at the end that I just can't find. Do you see it?
SELECT CASE
WHEN w.station_id = site_near.station_id THEN w.obs_id
ELSE s.obs_id
END AS obs_id, site_near.station_id, site_near.longname, w.year, w.doy
FROM site_near
INNER JOIN solar s
ON (site_near.ref_solar_station_id = s.station_id AND
site_near.obs_year = s.year)
INNER JOIN weather w
ON (site_near.ref_weather_station_id = w.station_id AND
site_near.obs_year = w.year AND s.date = w.date)
INNER JOIN (SELECT month, station_id,
round(avg(precip)::numeric, 2) AS avgprecip,
round(avg(tmin)::numeric, 2) AS avgtmin,
round(avg(tmax)::numeric, 2) AS avgtmax,
round(avg(par)::numeric, 2) AS avgpar,
FROM weather
GROUP BY month, station_id) AS avgclim
WHERE w.station_id = 219101;
On Aug 14, 2007, at 3:44 PM, Obe, Regina wrote:
> Yes I think you did or I missed something. Your subselects are
> going to return the average for the whole weather and solar tables
> (not for just that reference site) which doesn't quite seem like
> what you want if you are trying to put realistic placeholders for
> missing data in a site.
>
> Also I don't think you need to do 2 subselects for weather - I
> think you can combine into a single one with something like below
>
> (SELECT MONTH, station_id,
> round(avg(CASE WHEN precip != -999 THEN
> precip ELSE NULL END)::numeric, 2) AS avgprecip,
> round(avg(CASE WHEN tmax != -999 THEN tmax
> ELSE NULL END)::numeric, 2) AS avgtmax,
> FROM weather
> GROUP BY MONTH, station_id) As wmonthsummer
>
> Actually if you had put in NULLS for precip amd tmax instead of
> -999, you would be better off since those fall out of the equation
> quite nicely since aggregates completely ignore null.
>
> And then you could blissfully do
>
> (SELECT MONTH, station_id,
> round(avg(precip)::numeric, 2) AS
> avgprecip,
> round(avg(tmax)::numeric, 2) AS avgtmax,
> FROM weather
> GROUP BY MONTH, station_id) As wmonthsummer
>
> Hope that helps,
> Regina
>
> From: postgis-users-bounces at postgis.refractions.net [mailto:postgis-
> users-bounces at postgis.refractions.net] On Behalf Of Kirk Wythers
> Sent: Tuesday, August 14, 2007 4:25 PM
> To: PostGIS Users Discussion
> Subject: Re: [postgis-users] monthly climate query
>
> If I follow your point Regina (as far as the working daily query
> goes), I am returning data for a particular site based on the last
> line... WHERE w.station_id = some_valid_number.
>
> Did I miss something?
>
> On Aug 14, 2007, at 3:13 PM, Obe, Regina wrote:
>
>> Wouldn't you want to return the average for month for that
>> particular site? None of your month subselects seem to group by
>> station id. Would seem to me logically you should add station_id
>> to each of your subselects, group by station_id as well as month
>> and then your ON clause would be month and station_id.
>>
>> Hope that helps,
>> Regina
>>
>> From: postgis-users-bounces at postgis.refractions.net
>> [mailto:postgis-users-bounces at postgis.refractions.net] On Behalf
>> Of Kirk Wythers
>> Sent: Tuesday, August 14, 2007 12:15 PM
>> To: Discussion PostGIS Users
>> Subject: [postgis-users] monthly climate query
>>
>> I need some help with rewriting a query. I have a query that dumps
>> daily climate data, filling in missing data with monthly
>> averages (one line per day).
>>
>> I want to output monthly averages (one line per month). I am
>> having a hard time wrapping my head around this. Particularly how
>> to deal with the doy column (day of year). I have tried several
>> approaches and my forehead is starting to get my keyboard bloody.
>>
>> Here is the daily query:
>>
>> SELECT CASE
>> WHEN w.station_id = site_near.station_id THEN w.obs_id
>> ELSE s.obs_id
>> END AS obs_id,
>> site_near.station_id,
>> site_near.longname,
>> w.year,
>> w.doy,
>> --replace missing values (-999) with the monthly average
>> CASE w.tmax
>> WHEN -999 THEN avgtmax.avg
>> ELSE w.tmax
>> END,
>> CASE w.tmin
>> WHEN -999 THEN avgtmin.avg
>> ELSE w.tmin
>> END,
>> CASE s.par
>> WHEN -999 THEN avgpar.avg
>> ELSE s.par
>> END,
>> CASE w.precip
>> WHEN -999 THEN avgprecip.avg
>> ELSE w.precip
>> END
>> FROM site_near
>> INNER JOIN solar s
>> ON (site_near.ref_solar_station_id = s.station_id
>> AND site_near.obs_year = s.year)
>> INNER JOIN weather w
>> ON (site_near.ref_weather_station_id = w.station_id
>> AND site_near.obs_year = w.year
>> AND s.date = w.date)
>> INNER JOIN (SELECT MONTH,
>> round(avg(tmax)::numeric, 2) AS avg
>> FROM weather
>> WHERE tmax != -999
>> GROUP BY MONTH) AS avgtmax
>> ON (w.month = avgtmax.month)
>> INNER JOIN (SELECT MONTH,
>> round(avg(tmin)::numeric, 2) AS avg
>> FROM weather
>> WHERE tmin != -999
>> GROUP BY MONTH) AS avgtmin
>> ON (w.month = avgtmin.month)
>> INNER JOIN (SELECT MONTH,
>> round(avg(par)::numeric, 2) AS avg
>> FROM solar
>> WHERE par != -999
>> GROUP BY MONTH) AS avgpar
>> ON (s.month = avgpar.month)
>> INNER JOIN (SELECT MONTH,
>> round(avg(precip)::numeric, 2) AS avg
>> FROM weather
>> WHERE precip != -999
>> GROUP BY MONTH) AS avgprecip
>> ON (w.month = avgprecip.month)
>> --select station to output climate data by id number
>> WHERE w.station_id = 219101
>>
>>
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