How do I append my answers in an array, while using loop?

Question

Uche 2023-3-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1933630-how-do-i-append-my-answers-in-an-array-while-using-loop

编辑： Uche 2023-3-23

采纳的回答： VBBV

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Good day, please can someone help me with this problem?

In the code below, I want to add the following conditions:

Solve the equation 10 times using a "for" loop or while function. That is, have a variable L=10, and substrate 1 from it after each iteration. End loop, when L=0.
Create an array of two column vectors for the x and y values from each iteration, with x=6, and y=5 as the first values of this array. Similar to append.
Each solution of x and y, will be used as the z and w values for the next iteration.

z = 6;
w = 5;
syms x y 
eqn1 = x + y + z + w == 13;
eqn2 = 2*x + 3*y - w == -1;
sol = solve([eqn1, eqn2], [x,y]);
xSol = sol.x
ySol = sol.y

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Answer 1

VBBV 2023-3-23

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https://ww2.mathworks.cn/matlabcentral/answers/1933630-how-do-i-append-my-answers-in-an-array-while-using-loop#answer_1198820

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z = 6;
w = 5;
syms x y 
eqn1 = x + y + z + w == 13;
eqn2 = 2*x + 3*y - w == -1;
A = [6 5; zeros(10,2)];  % create matrix with x and y values as 
L = 10;
k = 2;
% using while loop
while L > 0
    sol = solve([eqn1, eqn2], [x,y]);
    xSol = (sol.x);
    ySol = (sol.y);
    A(k,:) = [double(xSol) double(ySol)];  % use double 
    Z = double(xSol);  
    W = double(ySol);
    syms z w x y;
    eqn1 = x + y + z + w == 13;
    eqn2 = 2*x + 3*y - w == -1;
    eqn1 = subs(eqn1,[z,w],[Z,W]);  % substitute new values for z and w in eqn1  
    eqn2 = subs(eqn2,[z,w],[Z,W]); % substitute new values for z and w in eqn2 
    k = k+1;
    L = L-1;
end
A  % final matrix with appended values 
A = 11×2
     6     5
     2     0
    34   -23
    30   -28
    62   -51
    58   -56
    90   -79
    86   -84
   118  -107
   114  -112

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Uche 2023-3-23

Amazing! Thank you.

Uche 2023-3-23

编辑：Uche 2023-3-23

在 MATLAB Online 中打开

@VBBV For this line, I would not want to specify a fixed number of columns (in this case 10). How can I leave the number of rows as a variable?

This is the problem I am having, if I specify 20, but run the 10 iterations, the first 10 positions are filled, the rest are returned as zeros. I don't want the zeros.

A = [6 5; zeros(10,2)]; % create matrix with x and y values as

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