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Jaewon

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Reply with quote  #26 
I still don't get it. Are those two subjects participating in the experiment together? If so, you can record the eye positions of the second subject via General Input, as you said, and manually calibrate them later. You don't have to calibrate before recording, since the second subject doesn't do trials during the experiment.
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kms

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Reply with quote  #27 
Yes, the two will be participating in the experiment together. How do you suggest I do manual calibration without reassigning Eye x and y? 

Thanks.
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Jaewon

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Reply with quote  #28 
You need to know the gaze angle and the voltage reading when the subject is looking at a particular point. Is there any fixation point or an object that the subject likes to watch? What is the subject doing during trials?
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kms

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Reply with quote  #29 
Thanks, Jaewon. The subject is free to look anywhere during the task but I want to make sure that all his saccades to an experimental area of interest [subject 1] are tracked well.

I think I now understand what you mean by manual calibration. I will give this a try though, of course, I will prefer something more automatic like the origin and gain method. 

Thanks.
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Jaewon

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Reply with quote  #30 
Eye position data saved in the BHV is calibrated numbers that are represented in degrees, not raw voltages. Since General Input doesn't get that kind of conversion, you have to do things manually.

You can still get the calibration parameters of the second subject easily with the calibration tools in ML. You just need to save it in a different CFG file. Make a copy of the conditions file and rename it with a different name so that your original _cfg.mat file is not overwritten. Then load that conditions file and revise I/O so that the X & Y channels of the second subject (that you previously assigned to General Input) are mapped to Eye X & Y on the menu panel. Then calibrate the eye signals of the second subject from there and save the settings. Now the calibration parameter of the second subject is in the new cfg file.

Then load the original conditions file and do the experiment. The eye signals of the second subject will be in the General input uncalibrated. Then you can read the second cfg file in MATLAB, get the origin and gain and apply them to the General Input signals. The locations of the origin and gain variables in the CFG are:

MLConfig.EyeTransform{2}.origin
MLConfig.EyeTransform{2}.gain

Does it make sense?
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kms

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Reply with quote  #31 
That sounds great; exactly what I was looking for as a work-around for my specific purpose without having to change the original ML code! 

Thanks a lot, Jaewon!
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Jaewon

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Reply with quote  #32 
FYI, the origin and gain calibration works like this.

degree = (voltage - origin) * gain
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