Re: missing values with month_to_seasonN

From: Adam Phillips <asphilli_at_nyahnyahspammersnyahnyah>
Date: Thu, 06 Sep 2007 16:15:06 -0600

Hi Will,
1)
Adam

Will Hobbs wrote:
> Adam
>
> Just to clarify what the correct behavior should be in the 'fixed'
> version, will it
>
> 1) Pass the _FillValue attribute from the input array to the output
> array, and set missing values in the output to that value
>
> or
>
> 2) Set the _FillValue attribute in the output array to the default (i.e.
> -999.) ?
>
> Will
>
> On Thu, 06 Sep 2007 15:57:30 -0600 Adam Phillips wrote:
>
>> Hi Will,
>>
>> I just created a test script looking into this and you're correct,
>> month_to_seasonN is labeling missing data as -999 but leaves the
>> _FillValue attribute the same as whatever it was when it was passed in
>> to the function... This is of course wrong, and will be fixed upon the
>> next release of NCL.. If anyone needs a corrected version of this
>> function let me know...
>>
>> Thanks for pointing this out.
>> Adam
>>
>> Will Hobbs wrote:
>>> Hi all
>>>
>>> This is just a comment on a problem that I'm having with the
>>> month_to_seasonN function. It may affect other functions but this is the
>>> first time I've come across it.
>>>
>>> I'm using SST from the hadisst dataset, which uses a _FillValue of
>> 1e+20,
>>> including land surface areas. See the following snippet, with
>> comments....
>>> x = f1->sst
>>>
>>> print(x@_FillValue) ;correctly returns 1+e20
>>> print(num(ismissing(x))) ; if the data includes land surface, this
>>> must be non-zero
>>>
>>> xSeas = month_to_seasonN(x, season)
>>>
>>> print(xSeas@_FillValue) ;returns 1+e20. fine
>>>
>>> print(num(ismissing(xSeas))) ;returns 0, wrong!
>>>
>>> print(num(xSeas.eq.xSeas@_FillValue)) ;again, incorrectly returns 0
>>>
>>> print(num(xSeas.eq.-999.)) ;returns a sensible answer
>>>
>>> Of course it's easy enough to fix a workaround for this..
>>>
>>> xSeas@_FillValue = -999.
>>>
>>> ...but if you're not aware of this it can cause some unusual results
>>> further down the line.
>>>
>>> Will
>>>
>>>
>>>
>>> ============================
>>> Will Hobbs
>>> PhD Candidate
>>> Room A113
>>> UCLA Department of Geography
>>> 1255 Bunche Hall
>>> Los Angeles CA 90095-1524
>>> Tel: 310 663 2631
>>>
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> ncl-talk_at_ucar.edu
>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>> --
>> --------------------------------------------------------------
>> Adam Phillips asphilli_at_ucar.edu
>> National Center for Atmospheric Research tel: (303) 497-1726
>> ESSL/CGD/CAS fax: (303) 497-1333
>> P.O. Box 3000
>> Boulder, CO 80307-3000 http://www.cgd.ucar.edu/cas/asphilli
>
>
>
> ============================
> Will Hobbs
> PhD Candidate
> Room A113
> UCLA Department of Geography
> 1255 Bunche Hall
> Los Angeles CA 90095-1524
> Tel: 310 663 2631
>

-- 
--------------------------------------------------------------
Adam Phillips			             asphilli_at_ucar.edu
National Center for Atmospheric Research   tel: (303) 497-1726
ESSL/CGD/CAS                               fax: (303) 497-1333
P.O. Box 3000				
Boulder, CO 80307-3000	  http://www.cgd.ucar.edu/cas/asphilli
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Received on Thu Sep 06 2007 - 16:15:06 MDT

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