Loop and element-by-element operation on table

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Ope 2018-5-31

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https://ww2.mathworks.cn/matlabcentral/answers/403373-loop-and-element-by-element-operation-on-table

评论： Ope 2018-6-1

Hello, I want to do element-by-element calculation on three tables, but I have two problems 1. with setting the loop correctly and 2. error on inner matrix dimension must agree. I will appreciate help to get my code working. Thanks.

% read constants
T0 = 0;             % temperature at the surface
Tm = 1300;          % temperature at base of plate
k = 0.000001;       % contant
alpha = 0.0000255;  % constant
rhom = 3300;        % density of the lithophere
L = 95;             % 0:5:120;
% read table data
h = load('t.txt');
t = load('a.txt');
rho = load('sf.txt');
% compute T iteratively
for h=1:20
    for t=1:20;
        for rho=1:20;
      a = (exp((-k*pi^2*t)./(L^2))*(sin((pi*h)./L)))+(0.5*exp((-k*4*(pi^2)*t)./(L^2))*(sin((2*pi*h)./L)))
      b = (h./L)+(2/pi)*a;        % first part
      T = T0 + (Tm - T0)*(d);     % main equation
      rho_t = alpha*rhom (Tm - T);    % density calculation 
      rho = rho_g - rho_t;        % density difference 
          end
      end
  end 
fid = fopen('out.dat','w');
fprint(fid,'%6.10f %6.10f 6.10f\n', T, rho_t, rho);
fclose(fid);

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Jan 2018-5-31

编辑：Jan 2018-5-31

Please post the complete error message. This is more efficient than guessing, which line causes the problem.

By the way: I do not see any tables in the code. Do you mean matrices? What is the contents of the loaded files? You overwrite the a,b,T, tho_t, rho in each iteration. In consequence you get one number from the last iteration only. Is this wanted? Seems to be a waste of time.

Ope 2018-6-1

Thanks Jan. I have attached 't.txt'. It is a single column matrix which is similar in content structure to a.txt, and sf.txt. I use it for testing the code.

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Answer 1

Paridhi Yadav 2018-5-31

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Hey, you have first loaded the values from text file in h, t and rho and then you have assigned them the value 1,2,3...20 so these variable now don't have the value you initially assigned them instead now they are a array of 1 to 20. And you are using 'd' which is not declared anywhere.

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Paridhi Yadav 2018-6-1

编辑：Paridhi Yadav 2018-6-1

在 MATLAB Online 中打开

Hey, you are only getting the value from last loop in T,rho_t and rho. Instead before running loop make a array of 20 for T, rho_t and rho. And use index i to store value in them just like we did to get the value of h and t.

        T(i) = T0 + (Tm - T0)*(b);     % main equation
        rho_t(i) = alpha*rhom (Tm - T(i));    % density calculation 
        rho(i) = rho_g - rho_t;        % density difference