For Loop/Nested Loop - using solution to previous iteration in nested loop?

Hello,

 I'm trying to do a nested loop in which from the second iteration onwards the term zl of the function being iterated is substituted by the solution to the previous iteration.  My code is underneath:

zl=(1/4.*((k.*a).^2))+(1j*0.6.*(k.*a));

%initiating loop

       for i=2:5
           for n=1:4

           x(i-1)=(0.077/4)*(i-1);  

           S(i-1)=St*(exp(m*x(i-1))); 

           Z(i-1,n)=(zl(n)+B(i-1,n))./((1+zl(n))./S(i-1).*C(n));      

           end
       end

So for the iteration 2 of Z, zl should corresponde to the first iteration of Z, for iteration 3 of Z, zl should correspond to the second iteration of Z and so forth. Hope I'm being clear. Any tips would be appreciated.

Answer 1

[Iman Ansari]

Hello

You want for example in n=3 iteration zl be Z computed in n=2 iteration? But with this line your zl is the same for all iterations:

   zl=(1/4*((k*a).^2))+(1j*0.6*(k*a));

You may need to write it before your loop:

%initiating loop
zl=(1/4*((k*a).^2))+(1j*0.6*(k*a));

for n=2:5

      x(n)=(0.077/4)*(n-1);         

      S(n)=St*(exp(m*x(n-1)));       

     %terms for equation Z

      A1=zl;
      B1=(1j*(p0c./(S(n-1)))).*(tan(k*L));
      C1=1;
      D1=(1j*(zl./(p0c/(S(n-1))))).*(tan(k*L));

       %equation Z composed of the previous terms
      Z=(A1+B1)./(C1+D1); 
      zl=Z;
end

[catarina]

Hi Iman,

Thanks for you reply. I re-edited the post as it wasn't clear plus I made some changes for the better I think. I did have the function you mention outside the loop but it didnt look like. Still can't figure out how to use previous solutions in the next iteration.

[Iman Ansari]

With this code you use 1:4 elements of zl or Z but I think your zl was a vector with 10000 elements.

Before end of the loop you can use zl=Z to set the value of zl in next iteration, like my code.

[catarina]

Thanks for your help. Much simpler than I thought. The vector should be 10000 or any length really, I should be able to change that. Now I'm having trouble in plotting the results. I would like the final results of Z but the graph looks a bit weird. I end up with a Z matrix of Z(4,10000) so I thought I should plot(Z(1,:)) to plot the results of the first row since my code goes from the 4th iteration to the first. Any tips? cheers