[gradsusr] Standard deviation of an area

Thu Nov 20 08:45:54 EST 2014

Hi David,

Thanks for your suggestion. I tried with the following
'reinit'
'open SSt12.precip.lon-lat.allssws.ctl'

'x1=1000*24*60*60*(aprl+aprc)'
while (count<1)
'set t' count
'define area=aave(x1,lon=120,lon=180,lat=-90,lat=90)
'd area'
'enable print figure1.zonalpre120-180E.mf'
'print'
'disable print'
'!./gxeps -c -i figure1.zonalpre120-180E.mf -o
SSt12.preci.120-180E.all.ssws.eps'
count=count+1
endwhile

but does not yield my result.

After running the script there is no error but the eps file produced is
blank.

Actually I want zonal average over longitude (120 to 180). The plot would
be X as time ( t=1 to t =21) and Y as latitude (90N to 90S). More over I
also want calculate statistical significance (t test values) over this plot
( may be in shaded).

Please help me

Sourabh

On Thu, Nov 20, 2014 at 2:00 PM, David Nielsen <davidnielsen at id.uff.br>
wrote:

> Julio,
>
> The way you suggested still returned a gridded result, not a number
> representig the area. Then I tried averaging the result over the same area
> (everything for each t-value):
>
>    define var1 = sqrt( pow( aave( sst, lat=..., lon=...)))
>    define var2 = aave( var1, lat=..., lon=...)
>
> Does it make any sense to you?
>
> Thanks again!
>
>
> Sourabh,
>
> So just checked, you can do:
>
> while (count < 22)
>    'set t' count
>    'define area = aave (variable-name, lon=120, lon=180, lat=-90, lat-90)
>    'd area'
>    count = count +1
> endwhile
>
> Works as fine as defining the area with x and y. Very small numerical
> difference though, don't know why.
>
> On 20 November 2014 10:23, David Nielsen <davidnielsen at id.uff.br> wrote:
>
>> Sourabh,
>>
>> You can try:
>>
>> while (count < 22)
>>    'set t 'count
>>    'define average=ave("variable-name", x and y limits)'
>>    'd average'
>>    count=count+1
>> endwhile
>>
>> You have to express lat and lon in terms of x and y in the "ave" formula.
>> For that, open the file in Grads and:
>>
>> set lat -90 90
>> q dim
>>
>> And it will tell you the equivalente x limits, for example.
>>
>> Not sure about this must, though. You can check it here:
>> http://www.iges.org/grads/gadoc/gradfuncave.html
>>
>> Hope it helps!
>>
>> Julio, I will try your suggestion now! Thanks again!
>>
>>
>> On 20 November 2014 09:39, Sourabh Bal <sourabhbal at gmail.com> wrote:
>>
>>> Hello David and Julio,
>>>
>>> if I want to plot time-latitude cross section (Y and T varying), with
>>> the data being averaged over longitude (120 to 180), where shall I fix
>>> the longitude.
>>>
>>> set lat -90 90
>>> set lon ??????
>>> set t 1 21
>>> d tloop(ave(aprl,lon=120,lon=180))
>>>
>>>
>>> Sourabh
>>>
>>>
>>>
>>> On Thu, Nov 20, 2014 at 1:35 AM, Julio Martinez <julioms24 at hotmail.com>
>>> wrote:
>>>
>>>> *David,*
>>>>
>>>> *Maybe you could try with*
>>>>
>>>> *d tloop(sqrt(pow(aave(uwnd,lon=200,lon=300,lat=0,lat=30),-uwnd,2)))*
>>>>
>>>>
>>>>
>>>>
>>>> Julio N. Martínez Sánchez
>>>> M.C. en Oceanografía Física
>>>> Consultor en Sitio
>>>> Subgerencia de Pronóstico a Mediano y Largo Plazo
>>>> Gerencia de Meteorología y Climatología
>>>> Servicio Meteorológico Nacional
>>>> Ext. 3156
>>>>
>>>>
>>>> ------------------------------
>>>> From: davidnielsen at id.uff.br
>>>> Date: Wed, 19 Nov 2014 21:13:14 -0200
>>>> To: gradsusr at gradsusr.org
>>>> Subject: Re: [gradsusr] Standard deviation of an area
>>>>
>>>>
>>>> Hi, Julio,
>>>>
>>>> My problem is not with the loop in time. I am using a "While" sintax to
>>>> execute the average along the series:
>>>>
>>>> while (count < "number of t-values +1")
>>>>    'set t 'count
>>>>    'define average=aave(sst,x=127.8,x=128.6,y=27.6,y=28.6)'
>>>>    'd average'
>>>>    average=subwrd(result,4)
>>>>    rc = write ("c:\path\file.txt",average)
>>>>    count=count+1
>>>> endwhile
>>>>
>>>> This is working fine. What I need now, is a way to calculate the
>>>> standard deviation of SST in the area of interest, also for each value of
>>>> t, like something independent of time, for me to insert inside the loop.
>>>>
>>>> Everything Ive seen before is a standard deviation of the whole series
>>>> (like below), and not for each time-value.
>>>>
>>>> 'define sdsst=sqrt(ave(pow(ave(sst,t=1,t=12)-sst,2),t=1,t=12))' ->
>>>> calculates std of the series between t=1 and t=2. What I'd like to do is,
>>>> for each t, an std of the area.
>>>>
>>>> Any suggestions?
>>>>
>>>> Thanks!
>>>>
>>>>
>>>> On 19 November 2014 13:38, Julio Martinez <julioms24 at hotmail.com>
>>>> wrote:
>>>>
>>>> *Hi David,*
>>>>
>>>>
>>>> *I think you could try with tloop command...*
>>>>
>>>> Julio N. Martínez Sánchez
>>>> M.C. en Oceanografía Física
>>>> Consultor en Sitio
>>>> Subgerencia de Pronóstico a Mediano y Largo Plazo
>>>> Gerencia de Meteorología y Climatología
>>>> Servicio Meteorológico Nacional
>>>> Ext. 3156
>>>>
>>>>
>>>> ------------------------------
>>>> From: davidnielsen at id.uff.br
>>>> Date: Wed, 19 Nov 2014 13:12:34 -0200
>>>> To: gradsusr at gradsusr.org
>>>> Subject: [gradsusr] Standard deviation of an area
>>>>
>>>>
>>>> Dear all grads users,
>>>>
>>>> I would like to calculate the standard deviation of an area in Grads.
>>>>
>>>> I have a NetCDF wekly time series of SST (attached), and I am able to
>>>> calculate the average of a certain area (defining LAT and LON) value using
>>>> the "aave" formula, for each value of time, and generate a new series - ok.
>>>> In addition to this seires, I would like to generate a series of standard
>>>> deviations of this average, also for each time in the series. In other
>>>> words, I need to to know, for a given area and time, what is the standard
>>>> deviation of my variable?
>>>>
>>>> Please find attached an example of a NetCDF file I want to treat this
>>>> way:
>>>> 1. Calculate average of SST in a certain area (lat, lon) using aave,
>>>> for each time value
>>>> 2. Calculate standard deviation of SST in a certain area (lat, lon),
>>>> for each time value
>>>>
>>>> Would anybody have any kind suggestions on how to address this #2 task?
>>>>
>>>> Many thanks in advance,
>>>>
>>>>
>>>>
>>>> --
>>>> David Marcolino Nielsen
>>>> Engenharia de Recursos Hídricos e do Meio Ambiente
>>>> Universidade Federal Fluminense
>>>> davidnielsen at id.uff.br
>>>>
>>>> _______________________________________________ gradsusr mailing list
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>>>>
>>>> _______________________________________________
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>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> David Marcolino Nielsen
>>>> Engenharia de Recursos Hídricos e do Meio Ambiente
>>>> Universidade Federal Fluminense
>>>> davidnielsen at id.uff.br
>>>>
>>>> _______________________________________________ gradsusr mailing list
>>>> gradsusr at gradsusr.org http://gradsusr.org/mailman/listinfo/gradsusr
>>>>
>>>> _______________________________________________
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>>>>
>>>>
>>>
>>>
>>> --
>>> Dr. Sourabh Bal
>>> Post-Doc Fellow
>>> Institute of Meteorology, Freie Universitat, Berlin
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> gradsusr mailing list
>>> gradsusr at gradsusr.org
>>> http://gradsusr.org/mailman/listinfo/gradsusr
>>>
>>>
>>
>>
>> --
>> David Marcolino Nielsen
>> Engenharia de Recursos Hídricos e do Meio Ambiente
>> Universidade Federal Fluminense
>> davidnielsen at id.uff.br
>>
>
>
>
> --
> David Marcolino Nielsen
> Engenharia de Recursos Hídricos e do Meio Ambiente
> Universidade Federal Fluminense
> davidnielsen at id.uff.br
>
> _______________________________________________
> gradsusr mailing list
> gradsusr at gradsusr.org
> http://gradsusr.org/mailman/listinfo/gradsusr
>
>

-- 
Dr. Sourabh Bal
Post-Doc Fellow
Institute of Meteorology, Freie Universitat, Berlin
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