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Topic: Polygraph manual set chart scale lower bound
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EMebane



Joined: Apr 15, 2019
Posts: 73

PostPosted: Jul 27, 2019 2:32 AM    Post subject: Polygraph manual set chart scale lower bound

How may I manually set the lower bound of the Polygraph element's scale? GainInteractor element allows auto setting, but I don't see anything in GainInteractor for manual settings. In Properties I can set the Amplitude Range, but that's just the upper bound.

My use case is I want to display 8-12 Hz dominant frequency over time so I want the chart's Y-axis to be 8-12. I can set the upper bound to 12 using Amplitude Range, but that leaves a range of 0-12 displayed, with a lot of unused space from 0-8.
jarek



Joined: Oct 22, 2007
Posts: 744

PostPosted: Jul 27, 2019 9:23 AM    Post subject:

You could use "Channel amplitude" max and min options. Those only set the scale (do not affect the signal), which means you need to make sure your input is properly rescaled for that range (which could be done easily in ExpressionEvaluator or RangeMapper).
EMebane



Joined: Apr 15, 2019
Posts: 73

PostPosted: Jul 27, 2019 12:12 PM    Post subject:

Thanks, that's what I needed. Those bonus Advanced properties!
EMebane



Joined: Apr 15, 2019
Posts: 73

PostPosted: Jul 28, 2019 4:02 PM    Post subject:

Actually, although the first Polygraph I used with Channel Amplitude settings is still working, a second Polygraph element is not. I explored the Vertical Axis min/max values and that seems more like what I was looking for, just control of the size of the value window on the vertical axis.

Would you describe what Channel Amplitude does in more detail? You say it "sets the scale" and doesn't affect the signal. Does that mean it sets the upper/lower limits of the vertical axis? That seems to be the same as what Vertical Axis min/max setting does.

I also see that Channel Amplitude can be used independently on each channel because it's an array. So I wonder if that means it is actually clipping the displayed values that are outside the specified range for each channel, but you said that it doesn't affect the signal so maybe this is done by affecting only the display of the signal and not the signal itself.
jarek



Joined: Oct 22, 2007
Posts: 744

PostPosted: Jul 28, 2019 5:42 PM    Post subject:

Yes, sorry, I made a mistake. What I said above was about "Vertical axis max/min" values.

The "Channel amplitude" does indeed rescale the signal. So it might be an easier option to use.
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