# [SOLVED]Cobb web Matlab

#### dwsmith

##### Well-known member
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:
%%% 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);