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VRF PEAK Detection

Question asked by VRFuser on Feb 4, 1998
> Subject:       VRF RE: PEAK Detection
> I need to obtain the time interval between peaks in a large array of
> data.

Ron,
I did just some litle thinking about your problem:

First you need to decide your threshold: what is a peak, what not.
For this playing with SIGNOF(SORT(ARRAY,0)-THRESHOLD) could help,
this will set the highest values first, and gives an array starting
with 1's for the peaks, -1's for the notpeaks. I realize that your
peaks might not be sigle values, but a range of values.
But still: choosing your threshold seems important.
Data filtering could help here.

Second I would map my array (I generated a coord array by filling
the Y-value with a ramp when I tried something). Then, when you
applied your threshold, after sorting the array it is fairly easy by
looking to the Y-values what is the time distance.

An FFT might be another way to find the repetition frequency (that is
in fact what you want to know)

At last: finding a good algoritm is important. Once found it,
programming is easy. Note that VEE is strong in manipulating arrays.
So not try to split up arrays too quickly.
With kind regards,
  Johannes Mulder           
  Philips Electron Optics            tel +31 40 2766867
  Building AAE-room 21               fax +31 40 2766820
  P.O.B. 218                  
  5600 MD ACHT, the Netherlands

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