[FieldTrip] ft_prepare_leadfield: no electrodes or gradiometers specified

[Kevin Lam]

Hi all,

I recorded EEG using BrainVision Recorder and have analyzed the data 
(ERP and TFR). Now, I would like to determine the source of the TFR 
effects. (I've been following, more or less, this procedure: 
http://fieldtrip.fcdonders.nl/tutorial/beamformer)

I'm having trouble executing ft_prepare_leadfield. Here's what I've done 
in the preceding steps, per participant:
  - ft_redefinetrial to specify the time of interest for each of the two 
conditions
  - ft_freqanalysis to calculate CSD matrix per the freq of interest for 
each condition
  - ft_volumesegment using 'spm' for coordsys
  - ft_prepare_headmodel using 'singlesphere' for method

Now, when I attempt ft_prepare_leadfield, I get an error saying 'no 
electrodes or gradiometers specified'. I understand what the function 
needs, but I don't have the input file it's asking for. It's not the 
.lay file - I gave this a try.

Please advise. Thanks in advance!

Regards,
Kevin