how to store Fibonacci iteration results?

Hello everybody

I would like to store the result of each iteration of the Fibonacci search algorithm.

if true
  function x=fibosearch(fhandle,a,b,npoints)
x  = [-50:10:20];
a1 = 0.2661;  
b1 = -18.24;  
c1 = 21.62;  
a2 = 1.135e+09;  
b2 =  1.174e+04;  
c2 =  2555;
fhandle = @(x)a1*exp(-((x-b1)/c1).^2) + a2*exp(-((x-b2)/c2).^2);
a=-50;
b=20;
npoints=100;
nfibo=22;
fibo=[1,1,zeros(1,nfibo-2)];
for k=1:nfibo-2
  fibo(k+2)=fibo(k+1)+fibo(k);
end
fiboindex=3;
while fibo(fiboindex)<npoints
      fiboindex=fiboindex+1;
end
for k=1:fiboindex-2
  if k==1
      x1 = a+fibo(fiboindex-k-1)/fibo(fiboindex-k+1)*(b-a);
      x2 = b-fibo(fiboindex-k-1)/fibo(fiboindex-k+1)*(b-a);
      fx1 = fhandle(x1);
      fx2 = fhandle(x2);
  end
if fx1<fx2
     a=x1;
     x1=x2; fx1=fx2;
     x2=b-fibo(fiboindex-k-1)/fibo(fiboindex-k+1)*(b-a);
     fx2=fhandle(x2);
  else
      b=x2;
      x2=x1; fx2=fx1;
      x1=a+fibo(fiboindex-k-1)/fibo(fiboindex-k+1)*(b-a);
      fx1=fhandle(x1);
end
end
if fx1<fx2
  x=x2;
else
  x=x1;
end
disp(fiboindex-2) 
end
end

The result of the final iteration is -16.0501624147 which is x. However, I would like to see the result of each iteration. How can I plot iteration number vs result of iteration?

Any help is highly appreciated.

Thanks

[madhan ravi]

format your code by clicking the code button

Answer 1

[Star Strider]

In your ‘k’ loop, add a line saving the appropriate value of ‘x1’ or ‘x2’ (or both, as I do here) along with the iteration number:

for k=1:fiboindex-2
    if k==1
        x1 = a+fibo(fiboindex-k-1)/fibo(fiboindex-k+1)*(b-a);
        x2 = b-fibo(fiboindex-k-1)/fibo(fiboindex-k+1)*(b-a);
        fx1 = fhandle(x1);
        fx2 = fhandle(x2);
    end
    if fx1<fx2
       a=x1;
       x1=x2; fx1=fx2;
       x2=b-fibo(fiboindex-k-1)/fibo(fiboindex-k+1)*(b-a);
       fx2=fhandle(x2);
    else
        b=x2;
        x2=x1; fx2=fx1;
        x1=a+fibo(fiboindex-k-1)/fibo(fiboindex-k+1)*(b-a);
        fx1=fhandle(x1);
    end
    xv(k,:) = [k x1 x2];                                                % <— Add This Line
end

That saves all of them to a matrix to work with later. (You will have to add that to the outputs of ‘fibosearch’ if you want to return it as an output.)

[engineer]

Thank you for your answer. How can I save this as output in to the workspace and plot them (iteration number vs x1 and x2 values?

[madhan ravi]

k = xv(:,1)

x1 = xv(:,2)

x2 = xv(:,3)

plot(k,x1) % k vs x1

 hold on

 plot(k,x2) %k vs x2

[engineer]

Thank you so much.

[Star Strider]

@engineer — As always, my pleasure.

@madhan ravi — Thank you.

(I was away for a few minutes.)

[madhan ravi]

@Star rider your welcome and keep inspiring as always :)

@engineer anytime