function [handler]=pfish2d(alphas,handler)% PFISH2D plots boundaries of Fisher's classifier in 2D.%  [handler]=pfish2d(alphas,handler)%% PFISH2D plots boundaries of the Fisher's classifier in 2D.%   See fishdemo for the example of use.%% Input:%  alphas [2xK] contains K vectors determining the classifer (cones).%  handler [...] contains handlers of used graphics objects.%% Output:%  handler [...] handlers to used graphics objects.%% See also FISHDEMO, FISHERP, FISHERK.%% Statistical Pattern Recognition Toolbox, Vojtech Franc, Vaclav Hlavac% (c) Czech Technical University Prague, http://cmp.felk.cvut.cz% Written Vojtech Franc (diploma thesis) 12.10.1999, 23.12.1999% Modifications% 26-June-2001, V. Franc, comments repared.% 24. 6.00 V. Hlavac, comments polished.alphas=alphas';% number of linesanum=size(alphas,1);%% Computes angles of the vectors alphas %%angles=[];for i=1:anum,   normal=norm(alphas(i,:));             % norm. vector alpha   if normal~=0,      alpha=alphas(i,:)/normal;      angle=acos(alpha(1));      if alphas(i,2) < 0,         angle=2*pi-angle;      end   else
      angle=0;
   end
   angles=[angles;angle];
end

%% Sort the alphas according to the angle %%
[angles,index]=sort(angles);
sortalphas=alphas;
for i=1:anum,
   if index(i) ~= i,
      sortalphas(i,:)=alphas(index(i),:);
   end
end
alphas=sortalphas;


if nargin == 1,
   % first tlotting, create lines
   % Get current axes
   window=axis;
   handler=zeros(anum*2,1);
   handler=[handler;gca];
   alpha0=alphas(anum,:);
   j=1;
   for i=1:anum,
      % draw border among the two vectors alpha
      alpha1=alphas(i,:);
      alpha=alpha0-alpha1;
      alpha=[-alpha(2) alpha(1)];
      [x,y]=cliplin2(alpha,window);
      handler(j)=line([0 x],[0 y],...
         'Color','k',...
         'EraseMode','XOR',...
         'LineStyle','--');
      j=j+1;

      % draw vector alpha
      [x,y]=cliplin2(alphas(i,:),window);
        %         'Color',XCOLORS(mod(index(i)-1,size(XCOLORS,2))+1),...
      handler(j)=line([0 x],[0 y],...
         'Color',color(index(i)),...
         'LineWidth',2,...
         'Marker','none',...
         'EraseMode','XOR');
      j=j+1;

      % If the alpha1 is equal to zero then don`t appear her.
      if sum(alpha1) == 0,
         set([handler(j-1) handler(j-2)],'Visible','off');
      end

      alpha0=alpha1;
   end

elseif nargin == 2,
   % second and/or latter plotting, update line properties

   window=getaxis(handler(size(handler,1)));;

   % plots decision boundaries and the vectrost alphas
   j=1;
   alpha0=alphas(anum,:);
   for i=1:anum,

      % plots decision boundary between two classes determined by the alphas
      alpha1=alphas(i,:);
      alpha=alpha0-alpha1;
      alpha=[-alpha(2) alpha(1)];
      [x,y]=cliplin2(alpha,window);

      % clear old line
      set(handler(j),'Visible','off');
      % plot new one
      if sum(alpha1) == 0,
         set(handler(j),'XData',[0 x],'YData',[0 y]);
      else
         set(handler(j),'XData',[0 x],'YData',[0 y],'Visible','on');
      end
      j=j+1;


      % computes line of the vector alpha
      [x,y]=cliplin2(alpha1,window);

      % clear old line
      set(handler(j),'Visible','off');

      % plot new line
      if sum(alpha1) == 0,
         set(handler(j),'XData',[0 x],'YData',[0 y],'Color',color(index(i)));
      else
         set(handler(j),'XData',[0 x],'YData',[0 y],'Color',color(index(i)),'Visible','on');
      end
      j=j+1;

      alpha0=alpha1;
   end
end