R help - Jul 2001 - ERP software

I was just playing around with the R-streams package, reading in some data
from an old experiment we did here, and was again amazed by the flexibility
of the R environment. The eaze with wich I was able to generate simple plots
of my EEG data made me wonder if someone tried to implement an ERP package.

For the non-cognitive scientists ou there: EEG is electrical activity
measured from the scalp (usually multi-lead) that is used in
psychophysiological experiments to infer cortical activation. In a typical
experiment this data can be linked to events: usually stimulus
presentations, to calculate 'trial means' in distict trial
subcategories.

Did someone out there made an effort to put together some sort of package
for the analysis of this type of data?


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----- Original Message -----
From: "Bill Simpson" <wsi at gcal.ac.uk>
To: "Mark M. Span" <span at psy.uva.nl>
Sent: Thursday, July 05, 2001 4:02 PM
Subject: Re: [R] ERP software

> No I haven't written any package to do EEG analysis. However I just
> started some expts with a colleague who uses Matlab for analysis. I will
> probably convert some of these into R so I can fool around with the data.
>
> I know that you can use Matlab to read the incoming data (from
> the A/D board) directly in realtime. Is that what R-streams is for??
> It would be handy to be able to use R both for the data collection phase
> and for the data analysis phase.
>
Rstreams reads in binary data (in the non-text meaning of binary). I guess
most of us (???) have dedicated software for data collection though..
We use a dataformat that is simple: all the data are written as two-byte
integers, channelwise.

reading in the data for analysis is a simple

 s <- openstream("U:/d1x001.eeg", "read")
 dat<-matrix(readint(s, n=33*3000000, size = 2, signed = F, swapbytes FALSE),
ncol=33, byrow=T)   # for 33 channel eeg, 3000000 datapoints (R
complaints about memory here)
 closestream(s)
 plot(dat[1:1000,31])  # plot the 31'th channel

The additional software would then cut up the matrix into (a list) of
trials...

almost looks too easy doesn't it...
> Cheers,
> Bill


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