binplot1(spot)

function binplot1(spot)
% BINPLOT1  plots a binomial tree matrix.  The matrix must
%           be square.  
%           
%           BINPLOT1(SPOT) where SPOT is the spot interest rates.
%           SPOT can be spot prices, interest rates, etc ...
%
%           For example :
% 
%           binplot1(binprice(52,50,.1,5/12,1/12,.4,0,0,2.06,3.5));

%   Author:       Ashesh Pansuria 
%   E-mail:       [e-mail]
%   Environment:  MATLAB 4.2c.1 in Windows 95                                           %

if length(spot) == 1
    error('Please check your spot (prices/rates)')
end

% Strip off the unwanted values
% of the binomial pricing matrix
% First create an index vector

j = 1;
index = 1;
for i = 1:length(spot):(length(spot) - 1).^2
    index = [index length(spot) + i : length(spot) + i + j];
    j = j + 1;
end
newspot = spot(index);

% Create 4 main vectors :
% (1) xvector - used for plotting dots and text
% (2) yvector - used for plotting dots and text
% (3) xvec    - used for connecting the dots
% (4) yvec    - used for connecting the dots

xvector = 1;
for i = 2:length(spot)
    xvector = [xvector i*ones(1,i)];
end    
vec = 0;
for i = 1 : length(spot)
    vec = [vec i:-2:-i];
end    
yvector = .5;
offset = .02;
for i = 1:length(xvector)
    yvector(i) = .5 + vec(i)*offset;
end    
for n=1:length(spot)
   temp = [n:n+1];
     for iter = 1:2*n
         xvec = [xvec temp];
     end
end
for i=1:2*length(yvector)
    dupyvector(i)=yvector(ceil(i/2));
end
for i = 1:2*length(dupyvector)
    dupdupyvector(i)=dupyvector(ceil(i/2));
end
for i = 1:length(dupdupyvector)
    if isodd(i) == 1
        yvec(i) = dupdupyvector(i);
    end
    if isodd(i) == -1
        if isodd(i/2) == 1
            yvec(i) = dupdupyvector(i) + offset;
        end
        if isodd(i/2) == -1
            yvec(i) = dupdupyvector(i) - offset;
        end
    end
end

% Set up the figure, x-axis limits
% y-axis limits

fig = figure( ...
        'Name','Tree Output', ...
        'NumberTitle','off', ...
        'Visible','on', ...
        'BackingStore','off');
set(gca,'Xlim',[0 length(spot)]);
set(gca,'Ylim',[0 1]);

% Plot the individual points and the
% corresponding text labels 

if length(spot) < 4
for i = 1:length(newspot)
    plot(xvector(i),yvector(i),'ro');hold on
    text(xvector(i) - .05,yvector(i) + .005,num2str(newspot(i)),'FontSize',10);
    hold on
    axis off
end
else
for i = 1:length(newspot)
    plot(xvector(i),yvector(i),'ro');hold on
    text(xvector(i) - .15,yvector(i) + .01,num2str(newspot(i)),'FontSize',8);
    hold on
    axis off
end
end

% Connect the individual dots

for i = 1:2:length(xvec) - (1 + 4*length(spot))
    plot([xvec(i),xvec(i + 1)],[yvec(i),yvec(i + 1)]);
    hold on
end