how can I save my error term in an array within while loop?

Question

mehmet salihi 2021-6-6

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/849095-how-can-i-save-my-error-term-in-an-array-within-while-loop

评论： SALAH ALRABEEI 2021-6-6

I am trying to save my Error term within While loop for this code in a list, could you please help me

thank you

clear
close all, clc
%Defining the constants
L=1;                                % length
H=2;                                % Height
deltax=0.05
deltay=0.05
Beta=deltax/deltay
Beta2=Beta^2
jn=H/deltay                         % Maximum number of grid points along y
im=L/deltax                         % Maximum number of grid points along x
T1=100; T2=0; T3=0; T4=0;           % boundary conditions
y=2:-deltay:0; x=0:deltax:L;
% initialize T_old to the initial guess values
T_old=zeros(jn+1,im+1);
% set boundary conditions
T_old(1,1:im+1)=T1; T_old(jn+1,1:im+1)=T3; T_old(2:jn+1,1)=T2; T_old(2:jn+1,im+1)=T4; T_new = T_old;
Error = 0.011;  % could be any number that is greater than Errormax
Errormax=0.01;
iter=0;
while Error > Errormax
    iter=iter+1;
    for i=2:jn 
        for j=2:im
            T_new(i,j)=(1/(2*(1+Beta2)))* (T_new(i-1,j)+T_new(i+1,j)+Beta2*(T_new(i,j+1)+T_new(i,j-1)) ) ;       
        end
    end
Error = sum(sum(abs(T_old-T_new),2))   ; 
T_old = T_new;
 
end
iter

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mehmet salihi 2021-6-6

thats sounds good, could you please tell how to save iterations also

my aim is to draw the iterations versus error history.

when i write the below command, i can see the error for each iterations,

disp([Error iter])

i want to plot them

thank you in advance

SALAH ALRABEEI 2021-6-6

在 MATLAB Online 中打开

the iteration starts from 1 and keeps increasing +1. So when the while iteration stops. Thus iter will be the maximum number of interations. So to plot the error,

    % 
  plot(1:iter,error)

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Answer 1

Scott MacKenzie 2021-6-6

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/849095-how-can-i-save-my-error-term-in-an-array-within-while-loop#answer_717965

编辑：Scott MacKenzie 2021-6-6

在 MATLAB Online 中打开

I haven't examined your code in any detail. However, if I understand your question correctly, you simply want to save all the error terms calculated in your loop in a list, probably so you can process them in some way after the loop finishes. In this case...

errorSave = [];
while ...
        
    Error = ...        
    errorSave = [errorSave Error];
    
end
% all the computed errors are in the vector errorSave