# Re: [visad] using ErrorEstimate

```Hi Tom,

```
That does appear to work as I would expect for Reals, so this does give me hope.
```
```
Now if I could just figure out if I can associate an error with each of my FlatField values without having to resort to a FieldImpl with a range of Reals.
```
Thanks,
Doug

Tom Whittaker wrote:
```
```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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