Re: Regarding 0 as a fill value

From: David Brown <dbrown_at_nyahnyahspammersnyahnyah>
Date: Wed Mar 17 2010 - 16:39:38 MDT

I would characterize this as a 'legacy feature' rather than a bug.
The low-level code that implements NCL contouring has a parameter that
sets the missing value for the contouring operation. Setting it to 0
(it's actually the default value) turns missing value detection off.
This is only true for contouring, not for vectors and streamlines.
   -dave

On Mar 17, 2010, at 4:16 PM, Dennis Shea wrote:

> Zero is a valid _FillValue
> [a] All functions and netCDF creation will have no problem.
> [b]
> It is "recommended" that users not use _FillValue = 0 if they want
> to perform certain contouring operations. The reason is that
> there is a historical bug in the contouring algorithm.
>
>
>
>
> On 03/17/2010 04:04 PM, Tong Qi wrote:
>> I'm sorry, I think I am not clear on the distinction between missing
>> value and _FillValue. When trying to plot a data field with 0 as the
>> _FillValue, I get the "warning:ContourPlotInitialize: 0.0 not
>> currently
>> supported as a missing value; expect inaccurate plot."
>>
>> On Wed, Mar 17, 2010 at 4:50 PM, Michael Notaro <mnotaro@wisc.edu
>> <mailto:mnotaro@wisc.edu>> wrote:
>>
>> 0 can be a fill value.
>>
>> For example,
>>
>> a=(/10,20,0,50/)
>> a@_FillValue=0
>> print(min(a))
>>
>> will output 10.
>>
>>
>>
>> On Mar 17, 2010, at 4:43 PM, Tong Qi wrote:
>>
>>> Hello,
>>>
>>> I am aware that the value of "0" is not currently supported as a
>>> fill value, but was wondering about the reason behind this. Could
>>> someone please clarify for me?
>>>
>>> Thanks,
>>> -Tong
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>
> --
> ======================================================
> Dennis J. Shea tel: 303-497-1361 |
> P.O. Box 3000 fax: 303-497-1333 |
> Climate Analysis Section |
> Climate & Global Dynamics Div. |
> National Center for Atmospheric Research |
> Boulder, CO 80307 |
> USA email: shea 'at' ucar.edu |
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Received on Wed Mar 17 16:39:44 2010

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