[c,h]=contoura(x,y,z,a,b),

function [c,h]=contoura(x,y,z,a,b),
% CONTOURA CONTOURA plot.
%       CONTOURA(Z) is a contour plot of matrix Z treating the values in Z
%       as heights above a plane.
%       CONTOURA(X,Y,Z), where X and Y are vectors and Z is a matrix, specifies
%       the X- and Y-axes used on the plot.
%       CONTOURA(X,Y,Z), where X, Y, and Z are vectors, interpolates
%       the data onto a rectangular grid.
%       CONTOURA(Z,N) and CONTOURA(X,Y,Z,N) draw N contour lines, 
%       overriding the default automatic value.
%       CONTOURA(Z,V) and CONTOURA(X,Y,Z,V) draw LENGTH(V) contour lines 
%       at the values specified in vector V.
%       CONTOURA(...,'linetype') draws with the color and linetype specified,
%       as in the PLOT command.
%
%       C = CONTOURA(...) returns contour matrix C as described in CONTOURC
%       and used by CLABEL.
%       [C,H] = CONTOURA(...) returns a column vector H of handles to LINE
%       objects, one handle per line. 
% 
%       NOTE: Do not rename this CONTOUR, it calls CONTOUR.
%       See also CLABEL, CONTOURC, CONTOUR3, GRADIENT, QUIVER, PRISM.

%       D. Thomas 11/17/94

A = 'xyzab';
C = ',,,, ';

args = [A(1:nargin);[C(1:nargin-1) ' ']];
args = [args(:)' ' '];

if (nargout == 1),
	argo = 'c=';
elseif (nargout == 2),
	argo = '[c,h]=';
else
	argo = '';
end 

if (nargin > 2)
	if (min(size(x)) == 1 & min(size(y)) == 1 & min(size(z)) == 1),
		
		if  ~(size(x(:),1) == size(y(:),1) & size(y(:),1) == size(z(:),1)),
			error('Sizes of X, Y, and Z must be equal');
		end
		xmin=min(x(:));
		ymin=min(y(:));
		xmax=max(x(:));
		ymax=max(y(:));
		N = ceil(length(x(:))^(1/2));
		Xl = xmin:((xmax-xmin)/(N-1)):xmax;
		Yl = ymin:((ymax-ymin)/(N-1)):ymax;
		[Xi,Yi]=meshgrid(Xl,Yl);
		Z = griddata(x,y,z,Xi,Yi);
		if (length(args) > 7),
			args = [',',args];
		end
		eval([argo,'contour(Xl,Yl,Z',args(7:length(args)),');']);
	else,
		eval([argo,'contour(' args ');']);
	end
else,
	eval([argo,'contour(' args ');']);
end