P300 Classifier GUI

Forum for discussion on different signal processing algorithms
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micsfox
Posts: 4
Joined: 24 Sep 2010, 12:10

P300 Classifier GUI

Post by micsfox » 24 Sep 2010, 13:03

How do milliseconds post stimulus map to the bins in “input element (bin)” of the linear classification matrix? The P300 classifier GUI outputs integer values, but the Offline Analysis tool for matlab results in real millisecond values for this bin. I know that it can the inclusion or not of “ms” after the number determines what units it’s in, but how does the classifier map the integer values back to the data?

gschalk
Posts: 615
Joined: 28 Jan 2003, 12:37

P300Classifier

Post by gschalk » 24 Sep 2010, 13:37

If you do not provide units in the classifier, just integers, then the classifier interprets them simply as indices into the signal matrix that is input to it.

In the case of the P3SignalProcessing module, the previous filter in the filtering chain is a waveform averaging filter. This filter spits out a matrix of dimension channel x sample, which is then input to the classifier. Thus, the units are units of samples, whose unit depends on the sampling rate. E.g., an index of 128 at 256 Hz sampling means 0.5 sec.

Gerv

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