elec_sph2cart.m

Matlab下的EEG处理程序库

function [X,Y,Z] = elec_sph2cart(theta,phi,r,angle)

% ELEC_SPH2CART - convert spherical to Cartesian coordinates
%
% Convert from spherical (theta,phi,r) to Cartesian rectangular (x,y,z)
% coordinates.
%
% Useage:   [X,Y,Z] = elec_sph2cart(theta,phi,r,angle)
%
%           theta is counterclockwise rotation from +x in x-y plane (azimuth),
%           phi is elevation with respect to Cz-axis,
%           r is radius,
%           angle = 1=radians (default) or 0=degrees for theta & phi
%
% Result:   (X,Y,Z) are double floating point
%           
% Note:     Conversion from spherical to Cartesian coordinates is:
%
%           x = r .* sin(phi) .* cos(theta);
%           y = r .* sin(phi) .* sin(theta);
%           z = r .* cos(phi);
%
%           +ve x-axis from origin through T4 (right ear)
%           +ve y-axis from origin through Nasion (at theta = +90degrees)
%
%           Results from this routine are not the same as those from
%           the inbuilt sph2cart matlab function. Phi here is 
%           elevation with respect to z-axis.  The matlab function 
%           sph2cart uses elevation with respect to xy plane.
%

% $Revision: 1.2 $ $Date: 2003/03/02 03:20:44 $

% Licence:  GNU GPL, no express or implied warranties
% History:  07/2001, [e-mail]
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

if ~exist('angle','var') angle = 1; end

if isequal(angle,0),
   % convert theta and phi to radians
   theta = theta * (pi/180); phi = phi * (pi/180);
end

X = r .* sin(phi) .* cos(theta);
Y = r .* sin(phi) .* sin(theta);
Z = r .* cos(phi);

return