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[IDV #MQM-696970]: visad error propagation facility

Hi Tyn-

> Further to my previous message, I already found some answers to some of my 
> questions. However, can you comment on the ??? below.
> 
> > What are the numerical equivalents for the other propagations methods to 
> > set int errorMode correctly?
> 
> Data.NO_ERROR    = 202
> Data.INDEPENDENT = ???
> Data.DEPENDENT   = ???

Data.INDEPENDENT = 200
Data.DEPENDENT   = 201

I've added the following to GridUtil so you can use them there:

    public static final int NO_ERRORS = Data.NO_ERRORS;
    public static final int DEPENDENT_ERRORS = Data.DEPENDENT;
    public static final int INDEPENDENT_ERRORS = Data.INDEPENDENT;

I've also added an error mode to the sampleToReal. sample already had the error 
mode signature.

These will be in tomorrow's build.

> http://www.unidata.ucar.edu/software/idv/docs/javadoc/constant-values.html#ucar.unidata.data.grid.GridUtil.DEFAULT_ERROR_MODE
> 
> > Is there a javadoc showing all propagations methods?
> 
> NO, except this snippet in 
> http://www.unidata.ucar.edu/mailing_lists/archives/visad/2002/msg00170.html:
> 
> 
> > Also, I can see that Data.INDEPENDENT uses a linear 'error
> > propagation' algorithm, but what does actually Data.DEPENDENT do (doesn't
> > one need to know the functional form of the dependency?). Is there any
> > auxiliary documentation somewhere, or references to the algorithms used?
> 
> For Data.DEPENDENT the system uses the worst case error
> propagation, where they are simply added. This is essentially
> interval arithmetic. For Data.INDEPENDENT the system uses
> root mean square error propagation.

I don't know any more than what was in that message.  As Bill pointed out, this 
has not been tested very well. I have no experience using the error 
propagation, but if you run into problems, we can muddle along together. ;-)

Don
 
> -----Original Message-----
> From: Unidata IDV Support [mailto:address@hidden]
> Sent: Wednesday, May 13, 2009 12:25 AM
> To: Valentijn Venus
> Cc: address@hidden
> Subject: [IDV #MQM-696970]: visad error propagation facility
> 
> Hi Tyn-
> 
> > thanks!
> >
> > Unfortunately, not everything is done with visad.
> 
> It will be difficult to do the error propagation fully then.
> 
> > On the IDV side, would it take a lot of work to for all methods to pass an 
> > error propagation type other than Data.NO_ERROR? Do you think Willem could 
> > handle such a task?
> 
> You'd need a way for the user to set the error mode and then modify all the
> methods in GridUtil that take a sampling method to also take an error mode.
> I took a stab at the latter, but not sure I got all the methods yet.  Then
> any of the controls/methods that do sampling would need to implement this
> as well.
> 
> I'm sure there are other gotcha's out there.  We're in the middle of
> finalizing the 2.7 release, so don't have time to work on this.  If
> Willem wants to look into it I can try to answer some of his questions.
> 
> Don
> 
> 
> Ticket Details
> ===================
> Ticket ID: MQM-696970
> Department: Support IDV
> Priority: Normal
> Status: Open
> 
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Ticket Details
===================
Ticket ID: MQM-696970
Department: Support IDV
Priority: Normal
Status: Open