Re: [visad] using ErrorEstimate

• To: "Doug Lindholm" <doug.lindholm@xxxxxxxxxxxxxxxxx>, "'visad@xxxxxxxxxxxxxxxx'" <visad@xxxxxxxxxxxxxxxx>
• Subject: Re: [visad] using ErrorEstimate
• From: "Tom Whittaker" <whittaker@xxxxxxxx>
• Date: Thu, 11 Dec 2008 12:43:22 -0600

Hi Doug --

In the Data Tutorial <http://www.ssec.wisc.edu/~tomw/visadtutor/visaddata.html>
there is a small section on Error Estimates (EE).  My understanding is
that you can associate
an EE with any Real, and when you combine some Reals together to make
a new Real, it will contain as estimate of the errors, based on the EE
in the original Reals and the math operations you've done to combine
them.

>From the tutorial:

    Real a,b,c;
    a = new Real(10.,1.);
    b = new Real(255.,10.);
    c = (Real) a.add(b, Data.NEAREST_NEIGHBOR, Data.INDEPENDENT);
    System.out.println("sum = "+c);
    System.out.println("error of sum is="+c.getError().getErrorValue());

When you run this example, you get:

    sum = 265.0
    error of sum is=10.04987562112089

The key, obviously, is to have an idea of the variance of your data....

Hope that helped...a little....

tom


On Wed, Dec 10, 2008 at 5:09 PM, Doug Lindholm
<doug.lindholm@xxxxxxxxxxxxxxxxx> wrote:
> Hi,
>
> I'm trying to figure out how to use ErrorEstimate-s. I have simple time
> series data as FlatField-s (time -> value) to do some math on and I'd
> like to propagate some errors. The reality is that I have an array of
> values and an array (of the same size) of variances.
>
> Do I need to construct an ErrorEstimate[] to pass to setRangeErrors? If
> so, how? I don't see a constructor that makes sense. I simply want to
> say, "here are the variances for each of my values."
>
> Thanks,
> Doug
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-- 
Tom Whittaker
University of Wisconsin-Madison
Space Science & Engineering Center (SSEC)
Cooperative Institute for Meteorological Satellite Studies (CIMSS)
1225 W. Dayton Street
Madison, WI  53706  USA
ph: +1 608 262 2759

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