[gradsusr] function

[Charles Seman]

Wendi,

Probably Examples 4 and 5 at 
http://grads.iges.org/grads/gadoc/gradfuncave.html might be more 
informative in terms of using a fixed dimension environment; especially 
note example 5:
---
The use of the define command can make certain operations much more 
efficient. If you want to calculate standard deviation, for example:

     sqrt(ave(pow(ave(z,t=1,t=20)-z,2),t=1,t=20))

     would be correct, but the inside average would be calculated 20 
times. Defining the inside average in advance will be substantially faster:

     define zave = ave(z,t=1,t=20)
     d sqrt(ave(pow(zave-z,2),t=1,t=20))
---

Chuck

On 07/11/2012 05:32 PM, Charles Seman wrote:
> Wendi,
>
> An idea; set the time dimension to span t=1,15 for the definition of "R":
>
> 'set t 1 15'
> 'R=pow((pow(10, ref/10))/200,5/8)'
> 'set t 1' ;* see discussion below
> 'd sum(R, t=1, t=15)'
>
> 'set t 1': for displaying sum; this is OK to go from time range to a
> single time level to do the sum (see "wild cards" discussion at
> http://grads.iges.org/grads/gadoc/variable.html#new); if left as 'set t
> 1 15', I think you would get 15 time levels with same "sum" result for
> the display command... you could try it both ways to see what you get...
>
> Hope this helps,
> Chuck
>
> On 07/06/2012 05:53 AM, wendi harjupa wrote:
>> Dear Grads users,
>>
>> I have problem,
>> below is  my descriptor file
>>
>> DSET /misc/home/wendi/data1/radar/kototabang/XDR/data/20040410/%d2%h2.dat
>> TITLE  RADAR
>> OPTIONS  TEMPLATE LITTLE_ENDIAN
>> UNDEF  -1000
>> XDEF    321 LINEAR    99.688120996    0.004492369
>> YDEF    321 LINEAR    -1.083708891    0.004522556
>> ZDEF    39  LINEAR   1.0 0.5
>> TDEF    15 LINEAR 21:00Z10apr2004  4mn
>> VARS    2
>> ref 39  99  Reflectivity(dBZ)
>> vel 39  99  Doppler Velocity(m/s)
>> ENDVARS
>>
>> As you see time is 15,
>>
>> I want to convert the ref (dbz) to Rain (mm/hr)
>> by using Z-R correlation formula, as below :
>>
>> 'pow((pow(10, R/10))/200,5/8)',
>>
>> Then I want to accumulate the rainrate for 1 hour,
>> I use this formula :
>>
>> 'sum(ref, t=1, t=15)'
>>
>> But I got strange result.
>>
>> Here my complete gs file,
>>
>> 'reinit'
>> 'set grads off'
>> 'set mproj latlon'
>> 'set mpdset hires'
>> 'set gxout shaded'
>> 'open RHI.ctl'
>> 'set lon 100 100.8'
>> 'set lat -0.45'
>> 'set Z 1 19'
>> 'set parea 1 7.5 2.8 8.3'
>> 'set clevs 0 50 100 150 200 250 300 350 400 450 500 550 600'
>> 'set ccols 9 14 4 11 5 13 3 10 7 12 8 2 6'
>> 'R=pow((pow(10, ref/10))/200,5/8)'
>> 'd sum(R, t=1, t=15)'
>> 'run /misc/home/wendi/grads-2.0.1/cbarn 0.7 0.7 7.9 5.2'
>> 'draw string  7.7 7.8 [dBz]'
>>
>> Would you help me, about this,
>> please let me know, which part I got wrong
>>
>> Thank you very much!
>>
>> Best regards,
>> wendi
>>
>>
>> --
>> -------------
>> Wendi Harjupa. ST
>> ShimaneUniversityGraduateSchool ofEngineering Sciences
>> Department ofElectronic ControlSystems
>> RemoteSensingLaboratory
>> s119447
>> Cellphone : +81-080-4268-6676
>> email : wendi at rslab.riko.shimane-u.ac.jp
>> <mailto:wendi at rslab.riko.shimane-u.ac.jp>
>>
>>
>>
>> _______________________________________________
>> gradsusr mailing list
>> gradsusr at gradsusr.org
>> http://gradsusr.org/mailman/listinfo/gradsusr
>>
>

-- 

Please note that Charles.Seman at noaa.gov should be considered my NOAA
email address, not cjs at gfdl.noaa.gov.

********************************************************************
  Charles Seman                                Charles.Seman at noaa.gov
  U.S. Department of Commerce / NOAA / OAR
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  201 Forrestal Road                              fax: (609) 987-5063
  Princeton, NJ  08540-6649            http://www.gfdl.noaa.gov/~cjs/
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