Getting Igor version 4 to trigger trains

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Sun, 08/01/2010 - 03:26 pm

Hi, I am running Igor version 4.01 and am using it to control a National Instruments data acquisition system (E-series board). I would like to get Igor to generate a pattern that can be either interval-based or event-based. Basically, the pattern is a train of pulses, with the inter-pulse intervals varying across time in a Poisson manner. Does anyone have a procedure file or whatever program that would enable me to specify in Igor 4 such kinds of stimulus patterns? I would also appreciate any suggestions or tips on how to modify code in Igor 4 to do that as well. Thanks.
Use the waveform generator and fill a wave with the pulse pattern you want, then generate a waveform using that pattern. If you can't do that, please provide some more details.

That's a very old version of Igor :)

John Weeks
WaveMetrics, Inc.
support@wavemetrics.com

August 2, 2010 at 04:47 pm - Permalink

Here is a crude function to get you started in generating the Poisson pulse pattern. It assumes that the probability of having a pulse in a given wave deltax, lambda*deltax, is <<1. As well as creating the Poisson pulse wave, the function also returns, as a rough check, the trial's estimate of the arrival rate (lambda) from the number of trial pulses.
function poisson(lambda, npts, dx)  // lambda=probability per unit time; npts=numpnts(wave0)
    variable lambda, npts, dx   // dx=wave deltax scaling
    make/O/N=(npts) wave0
    setscale/P x, 0, dx,"" wave0
    wave0   = abs(enoise(1))<(lambda*dx) ? 1 : 0
    return sum(wave0)/(npts*dx)
end

From this you should be able to generate the DAQ wave you need. If you need wider output pulses, be careful that your lambda is small enough so they have a small probability of overlapping. If Igor 4 does not have the conditional assignment syntax, you can make your own (if, else) equivalent.

August 4, 2010 at 09:22 am - Permalink