query on channel arrangement

Robert Oostenveld r.oostenveld at FCDONDERS.RU.NL
Mon Feb 27 10:05:56 CET 2006

Dear Muthu

FieldTrip always works with channel labels, not with channel numbers.
All functions, e.g. freqdescriptives (which computes coherence) or
the plotting functions use the labels. The channel labels are read
from the datafile, if the datafile does not include the correct
channel labels, you have to fix them yourself. Do that after
preprocessin, i.e. after preprocessing you can change the data.label
cell array. From then on, FT will not look in the data file any more,
so the channnel labels will remain as you have renamed them.

The freqanalysis or freqdescriptives function do not care where each
channel is, they only care about the channelcombiations that you
specify between which to compute coherence. The plotting functions of
course do need to know where each channel is, otherwise it cannot
plot. The information about the channel locations is stored in the
layout file, which is an ascii text file with the extension *.lay.
You should have a look in the elec1010.lay file, which probably is
already pretty close to teh layout that you want to use.


On 23-feb-2006, at 11:32, Muthuraman Muthuraman wrote:

> We have the data for EEG taken with 64-channel(Neuroscan) arrangement
> and i need to specify channel arrangement
> when i want to calculate the coherence between EEG and EMG
> so for example : in real data
> FPZ- 45 -in the EEG channel arrangement
> AF7-41 -in the EEG channel arrangement
> M1-29- EMG channel
> M2-30-EMG channel
> M3-63-EMG channel
> M4-64-EMG channel
> but when i calculate the coherence i want them in the 64-channel
> layout
> instead of 151 layout
> and to change the channels in the coherence plot as
> for example-
> FPZ-1 -in the coherence plot
> AF7-2 -in the coherence plot
> M1-52-in the coherence plot
> M2-53-in the coherence plot
> M3-54-in the coherence plot
> M4-55-in the coherence plot
> Like this i wanted to change the channel arrangement in the
> coherence plot for all the channels
> how can i change it, please  can you give me some idea regarding this

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