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Homework Help: Cobb web Matlab

  1. Feb 24, 2012 #1
    I found some Matlab code that works. However, I am not sure how to alter it for my needs.

    How can I make the code work for this:

    $$N_{t+1} = \frac{(1+r)N_t}{1+rN_t}$$

    What needs to be changed?
    Code (Text):
    %%% MAKES A COBWEB PLOT FOR A LOGISTIC MAP

    % compute trajectory
    a=3.0;          % parameter
    x0=0.2;         % Initial condition
    N=40;           % Number of iterations
    x(1) = x0;    
    for ic=1:N
     x(ic+1) = a*x(ic)*(1-x(ic));
    end




    % plot the map function and the line y=x
    clf;
    t = 0:0.01:1;
    plot(t,a*(t.*(1-t))); hold on;
     axis('square'); axis([0 1 0 1]);
     set(gca,'XTick',(0:0.1:1),'YTick',(0:0.1:1))
     grid on;


     fplot('1*y',[0 1],'r');



    %%%%%% STEP 3: PLOT COBWEB
     line([x(1) x(1)],[0 x(2)],'Color','g')
      plot(x(1), x(1),'ko');
     for ic=1:N-1
      line([x(ic) x(ic+1)],[x(ic+1) x(ic+1)],'Color','g')  
      line([x(ic+1) x(ic+1)],[x(ic+1) x(ic+2)],'Color','g')
      plot(x(ic+1), x(ic+1),'ko');
     end
     line([x(N) x(N+1)],[x(N+1) x(N+1)],'Color','g')
     
       %%%%%% STEP 4: SIGN THE PLOT
     at=text(0.1,0.82,['a=',num2str(a)]); set(at,'FontSize',12);
     
  2. jcsd
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