Removing channel

Discussions
1

Hi,
Is there a procedure in brainstorm that removes channels from the file?
I know that bad channels can be marked but I want to completely remove redundant channels from the data structure.

Best
Nir

2

Hi Nir,

No, there is no easy way to remove a channel of data from the interface.
The best way to get rid of a channel in the analysis is to change its type. See this example:
http://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy#Access_the_recordings

You can do it manually by editing all the structures by yourself. You need to edit the channel file (remove the corresponding entry in .Channel) and in the recordings (remove the corresponding rows in .F and .ChannelFlag).
You need to do this before you compute any SSP or ICA projectors.
http://neuroimage.usc.edu/brainstorm/Tutorials/ChannelFile#On_the_hard_drive
http://neuroimage.usc.edu/brainstorm/Tutorials/Epoching#On_the_hard_drive

Francois

3

Thank you very much.
In my efforts to remove channels from the data I attempted to utilize the run Matlab code in the “pre-procesing” category of the pipline editor.
The code I was attempted for the removal of the last two rows of data was

Data = Data(1:end -2, :);

Bet I got a subscript out of range error.

My question for that description is: what is the nature of this procedure and the Data variable?
It is important to me because I might want to use it for some more sophisticated analysis.

Best,
Nir

4

This process “Run Matlab command” cannot change the size of the Data variable. Therefore you cannot delete a channel with it. You have load the channel and data files, modify them and save them back. You can use either the popup menus File > Export from Matlab / Import from Matlab, or the reading functions (in_bst_data / in_bst_channel) and writing functions (bst_save).

Again, I strongly discourage this procedure.
There is usually no reason to edit the list of channels, it will have exactly the same effect if you simply change the type of the channels you want to get rid of (right-click > Edit channel file). Just enter a type that you will not use (for instance “other” or “ignore”…)

If your goal is to have the same list of channels for multiple subjects or acquisition sessions, use the process “Standardize > Uniform list of channels” instead.

5

Thanx
Altering the channel arangement data is a good solution.

nir