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numerical integration of unevenly spaced data

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```Hello all,

Is there a VI (or does anybody have one) that can integrate unevenly
spaced numerical data?  I know the basic numerical integrator only
works for evenly spaced data (data spaced at a constant interval)..

Thanks for youe help....

Jay  Poret, Ph.D.
AOT, Inc.
```
 0
Reply x9561 (148656) 6/5/2004 4:51:20 AM

See related articles to this posting

```Help for the Numeric Integrator.vi shows the formulas.  For the
trapezoidal rule (the simplest one) the integral is the sum of partial
sums which are given by: 1/2(x[i] + x[i + 1])*dt.

If you change dt to dt(i) = t[i+1] - t[i], I think this should give
you a reasonable approximation. The more complex rules cannot use this
approach.  The trapezoidal rule simply sums the area under the
trapezoids created by connecting the t[i], x[i], x[i+1], t[i+1] dots,
so this change should not introduce any errors.
```
 0
Reply x9561 (148656) 6/7/2004 7:03:07 PM

```John,

Thanks for the reply...I believe I solved the problem by creating a VI
based on fitting my data with a cubic spline and then generating new y
data based on evenly spaced x data.  It actually works pretty well..
The trick is to use the two cubic spline Vis in the processing
tools....
```
 0
Reply x9561 (148656) 6/8/2004 3:08:45 AM

```Radman,  could you go into more detail on what it is you are doing
here?  This is exactly what I want to do and I'm not sure what you are
talking about by using two cubic spline VI's
```
 0
Reply x9561 (148656) 9/9/2004 9:27:31 PM

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