MATLAB: How to store each iteration value and plot it

fibonacci

Hi everyone I would like to store each L2 values after each iteration and plot it vs iteration number. How can I do it with the attached code?
clc;
clear all;
n=input('Enter the no of iterations : \n');
N=n+1;
a=input('\n Enter lower limit : \n'); 
b=input('\n\nEnter upper limit : \n');
fold=1;
fnew=1;
func = @(x)(.65-[.75/(1+x^2)]-.65*x*atan(1/x));
for i=1:N
  if i==1 || i==2
    f(i)=1;
   continue;
  end
  f(i)=fold+fnew;
  fold=fnew;
  fnew=f(i);
end
L2=(b-a)*f(N-2)/f(N);
j=2;
while j<N
  L1=(b-a);
  if L2>L1/2
    anew=b-L2;
    bnew=a+L2;
  else 
    if L2<=L1/2
      anew=a+L2;
      bnew=b-L2;
    end
  end
  k1=func(anew);
  k2=func(bnew);
  if k2>k1
    b=bnew;
    L2=f(N-j)*L1/f(N-j+2);
  else 
    if k2<k1
      a=anew;
      L2=f(N-j)*L1/f(N-(j-2));
    else 
      if k2==k1
        b=bnew;
        L2=f(N-j)*[b-a]/f(N-(j-2));
        j=j+1;
      end
    end
  end
  j=j+1;
end
disp(a);
disp(b);

Best Answer

Preallocate for L2 and keep and increment an index inside the loop and store into an array
L2=zeros(N,1);                % preallocate
L2(1)=(b-a)*f(N-2)/f(N);      % save initial value
j=2;
while j<N
  L1=(b-a);
  if L2>L1/2
    ...
every store is then
L2(j)=...;
Or, change to counted for loop instead of while since there's no conditional exit.
L2(1)=...;
for j=2:N-1
  ...
  L2(j)=...;
  ...
BTW, Matlab "elseif" is one string, I had to reformat code to try to read it for indention levels being all fouled up where you wrote
...
else if L2<=L1/2
  ...
Rewrite
if L2>L1/2
  anew=b-L2;
  bnew=a+L2;
else 
  if L2<=L1/2
    anew=a+L2;
    bnew=b-L2;
  end
end
as
if L2>L1/2
  anew=b-L2;
  bnew=a+L2;
elseif L2<=L1/2
  anew=a+L2;
  bnew=b-L2;
end
which since the 'elseif' is the negation of the 'if' condition, this is really
if L2>L1/2
  anew=b-L2;
  bnew=a+L2;
else 
  anew=a+L2;
  bnew=b-L2;
end
there's no need for the conditional if on the else clause here.
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