bci2000.org BBS

Hello

I am experiencing problem in converting eeg signal in the format .mat
into any format that supported by the bci2000 offline analysis toolbox
I will be pleased if someone help me

Elgasim

In order to save data as a BCI2000 data file, you will need to provide parameter and state (event, trigger) information in a suitable format, and then use the save_bcidat mex file to write out the file.

Could you give more information about what you want to do?

--Juergen

can you tell me more about the parameters and triger events and how can i add it to the data?

What kind of data do you have? Sensorimotor rhythms, or evoked potentials?

My data is berlin bci competition IV data set one "(seven subjects imagining three types of movement right hand, left hand, and leg movement) utilizing motor imagery

You will need to specify target conditions for each point in time. Create a struct variable "states" with a member "StimulusCode" in Matlab, which is a N x 1 matrix. It should have as many entries as there are samples in the data set. For each point in time, assign a StimulusCode of 0, 1, 2, or 3, depending on which imagination was performed at that point in time:

• 0 when no imagination was performed,
  1 when right hand movement was imagined,
  2 during left hand imagination,
  3 during leg movement imagination.

In addition, you need to specify the sampling rate as a BCI2000 parameter. In Matlab, create a struct variable "parameters", with a member "SamplingRate", which is itself a struct, with the following fields (replace the number in the Value field with the actual sampling rate):
Assuming that the EEG signal is contained in a variable called "signal" with dimensions channels x samples, run the following command:

save_bcidat('myfile.dat', signal, states, parameters);

The resulting file should be suited for use with the BCI2000 OfflineAnalysis program.

I had constructed the structures states,parameters with their substructures stimuluscode, samplingrate respectively but,when using the command:
save_bcidat('myfile.dat', signal, states, parameters);
returns:
??? Error using ==> save_bcidat
Parameter values must be strings or cell arrays of strings.

and when i convert the parameters.sampling rate into cell using the command:
struct2cell
it returns:
??? Error using ==> save_bcidat
Could not access string field "Section".
would yu help me please

Did you enclose the parameter value into curly braces as in ?

yes i wrote the code:
SamplingRate= struct('Section','Source','Type','int','DefaultValue','256Hz','LowRange','1','HighRange','','Comment','sample rate','Value',{'100'},'NumericValue','100');

yes i wrote the code:
SamplingRate= struct('Section','Source','Type','int','DefaultValue','256Hz','LowRange','1','HighRange','','Comment','sample rate','Value',{'100'},'NumericValue','100');
but, the problem is still running

When you write what does the output look like?

the code looks like:
>> parameters.SamplingRate

ans =

Section: 'Source'
Type: 'int16'
DefaultValue: '256Hz'
LowRange: '1'
HighRange: ''
Comment: 'sample rate'
Value: '{100}'
NumericValue: '100'


and when using the command struct2cell it looks like;
>> parameters.SamplingRate

ans =

'Source'
'int16'
'256Hz'
'1'
''
'sample rate'
'{100}'
'100'

Look at the curly braces in the "Value" field. The field should read {'100'} but it reads '{100}'. Once you correct this, it should work.