arrow3.m

用matlab实现利用统计混沌方法解决非线性系统时间序列预测的问题

function arrow3(point1,point2,S,rlength,rwidth)
% The function: 
% 
%       arrow(point1,point2,S,rlength,rwidth)
% 
% draws an arrow from point <point1> to point <point2>
% in the 3-dimensional space. 
% Optional arg <S> is like in plot3(X,Y,Z,S); 
% default value is '-'.
% Optional arg <rlength> is the relative length of the 
% pointing end; default value is 0.3. 
% Optional arg <rwidth> is the relative width of the 
% pointing end; default value is 0.2. 

% args
if nargin<2, error('not enough args'); end;
if nargin<3, S = '-'; end;
if nargin<4, rlength = 0.3; end;
if nargin<5, rwidth  = 0.2; end;

% base arrow
arrowx = [0,1,1.0-rlength,1,1.0-rlength];
arrowy = [0,0,+0.5*rwidth,0,-0.5*rwidth];
arrowz = [0,0,          0,0,          0];

% vector
v = point2 - point1;
if length(v)==3,
        if size(v,2)==3, v = v'; end;
end;

% dilation, rotation & plot
if length(v)==3,
        n = norm([v(2),v(3)]);
        if n==0,
                % not rot needed
                arrowxyz = v(1) * [arrowx;arrowy;arrowz];
        else,
                % rot around x axis
                drot23 = [[      1,      0,      0];
                          [      0,+v(3)/n,-v(2)/n];
                          [      0,+v(2)/n,+v(3)/n]];
                v = drot23*v;
                
                % norm of rotated vector
                n = norm([v(1),v(3)]);
                
                % rot around y axis
                drot13 = [[+v(1)/n,      0,+v(3)/n];
                          [      0,      1,      0];
                          [-v(3)/n,      0,+v(1)/n]];
                v = drot13*v;
                arrowxyz = norm(point2-point1)*drot23'*drot13'*[arrowx;arrowy;arrowz];
        end;
        
        plot3(point1(1)+arrowxyz(1,:),point1(2)+arrowxyz(2,:),point1(3)+arrowxyz(3,:),S);
end;