headplot() - Plot a spherically-splined EEG field map on a semi-realistic 
              3-D head model. Rotate head using left mouse button. Uses spline
              interpolation of Perrin et al., Electroenceph Clin Neurophys, 1989

                                Example
 Usage:

(Info)    >> headplot('example'); % show an example 'eloc_angles' file
(Do once) >> headplot('setup','eloc_angles','splinefile','comment','type');

 Inputs:

     'eloc_angles' - file of electrode locations in spherical coords.
                       See functions: cart2topo() and topo2sph()
     'splinefile'  - name of spline file to save splining info into
     'comment'     - optional string vector containing info for spline file
     'type'        - type of electrode locations file ('cartesian' or default
                     'spherical')

 (Thereafter )  >> headplot(values,'spline_file','Param','Value',...);

 Inputs:

     values       - vector containing value at each electrode position
    'spline_file' - spline filename computed and saved by running 'setup'

 Optional Parameters (any order)  & Values

     'title'      -  Plot title {default none}
     'electrodes' - 'on'|'off' -> show electrode positions {default 'on'}
     'labels'     -  2 -> plot stored electrode labels;
                     1 -> plot channel numbers; 0 -> no labels {default}
     'cbar'       -  0 -> Plot colorbar {default: no colorbar}
                     H -> Colorbar axis handle (e.g., choose location)
     'view'       - Camera viewpoint in deg. [azimuth elevation]
                     'back'|'b'=[  0 30]; 'front'|'f'=[180 30] 
                     'left'|'l'=[-90 30]; 'right'|'r'=[ 90 30];
                     'frontleft'|'bl','backright'|'br', etc.,
                     'top'=[0 90]   {default [143 18]}
     'maplimits'  - 'absmax' -> make limits +/- the absolute-max
                     'maxmin' -> scale to data range
                     [min,max] -> user-definined values
                     {default = 'absmax'; red +, blue -, green 0}
     'lights'     - (3,N) matrix whose rows give x,y,z pos. of 
                      N lights {default: 4 lights at corners}
     'lighting'   - 'off' = show wire frame {default 'on'} 
     'colormap'   -  3-column colormap matrix {default jet(64)}
     'verbose'    - 'off' -> no msgs, no rotate3d {default 'on'}


                                                       Toolbox function list


Colin Humphries & Scott Makeig, 2/98