tersurf.m

function [hg,htick,hcb]=tersurf(c1,c2,c3,d)
%FUNCTION [HG,HTICK,HCB]=TERSURF(C1,C2,C3,D) plots the values in the vector d 
% as a pseudo color plot in a ternary diagram.
% The three vectors c1,c2,c3 define the position of a data value within the
% ternary diagram.
% The ternary axis system is created within the function.
% Axis label can be added using the terlabel function.
% The function returns three handels: hg can be used to modify the grid lines,
% htick must be used to access the tick label properties, and hcb is the handle
% for the colorbar.
%
% Uli Theune, Geophysics, University of Alberta
% 2002 - ...
%

if nargin < 4
    error('Error: Not enough input arguments.');
    return
end
if (length(c1)+length(c2)+length(c3))/length(c1) ~=3
    error('Error: all arrays must be of equal length.');
    return
end

% Check if the data need to be normalized
if max(c1+c2+c3)>1
    for i=1:length(c1)
        c1(i)=c1(i)/(c1(i)+c2(i)+c3(i));
        c2(i)=c2(i)/(c1(i)+c2(i)+c3(i));
        c3(i)=c3(i)/(c1(i)+c2(i)+c3(i));
    end
end

hold on
% Calculate the position of the data points in the ternary diagram
x=0.5-c1*cos(pi/3)+c2/2;
y=0.866-c1*sin(pi/3)-c2*cot(pi/6)/2;

% Create short vectors for the griding
tri=delaunay(x,y);
trisurf(tri,x,y,d);
shading interp

% Add the axis system now
d1=cos(pi/3);
d2=sin(pi/3);
l=linspace(0,1,6);
zmax=max(d);
for i=2:length(l)-1
   hg(i-1,3)=plot3([l(i)*d1 1-l(i)*d1],[l(i)*d2 l(i)*d2],[zmax zmax]*1.1,':k','linewidth',0.25);
   hg(i-1,1)=plot3([l(i) l(i)+(1-l(i))*d1],[0 (1-l(i))*d2],[zmax zmax]*1.1,':k','linewidth',0.25);
   hg(i-1,2)=plot3([(1-l(i))*d1 1-l(i)],[(1-l(i))*d2 0],[zmax zmax]*1.1,':k','linewidth',0.25);
end
plot([0 1 0.5 0],[0 0 sqrt(3)/2 0],'k','linewidth',1)
% Make x-tick labels
for i=1:length(l)
    htick(i,1)=text(l(i),-0.025,num2str(l(i)));
    htick(i,3)=text(1-l(i)*cos(pi/3)+0.025,l(i)*sin(pi/3)+0.025,num2str(l(i)));
    htick(i,2)=text(0.5-l(i)*cos(pi/3)-0.06,sin(pi/3)*(1-l(i)),num2str(l(i)));
end
hold off
axis image
axis off
caxis([min(d) max(d)])
view(2)
hcb=colorbar;