How to calculate in one or many matrices based on other matrix?

Dear all,

I'm having these two matrices:

A = [ In - I2 B = [ C1 + 2G2 0

- I1 2G1 0

- I3 - 2G1 - 2G2 0

- I1 0 C2

- I4 0 2G3

- I2 ] 0 -2G3 ]

And I want to make a for loop to subtraction the same elements of matrix A and matrix B will subtraction with the same row of matrix A.

Example:

A(1,:) = In - I2 so I A(1,:) - A(6,:) = In - I2 - (- I2) = In and i want B do the same way.

A(6,:) = - I2

The result is like this:

A = [ In B = [ C1 + 2G2 2G3

0 2G1 -C2

-I3 - 2G1 - 2G2 0

-I4 ] 0 2G3 ]

Please give me some suggests and functions. Thank you very much.

[KSSV]

How symolic terms/ variables are present in matrix? How you got these matrices?

[Nguyen Hoang Hai]

I defined symbolic variables and created some matrices with them. Matlab's matrix calculus is powerful, I want to use matlab to compute symbolic matrices.

[Jan]

I do not understand this sentence: "And I want to make a for loop to subtraction the same elements of matrix A and matrix B will subtraction with the same row of matrix A."

If you post the code you use to create A and B, it is much easier to create an answer.

[Nguyen Hoang Hai]

I defined variables and created matrices like this:

syms In I1 I2 I3 I4 C1 C2 G1 G2 G3

A = [In - I2;-I1;-I3;-I1;-I4;-I2]

B = [C1+2*G2,0;2*G1,0;-2*G1-2*G2,0;0,C2;0,2*G3;0,-2*G3]

Example I check elements of matrix A, A(1,:) = In - I2 and A(6,:) = - I2, both of them include element I2, and then I do subtraction to get the result A(1,:) - A(6,:) = In - I2 - (- I2) = In. Base on that, matrix B do the same subtraction with B(1,:) and B(6,:) at the same time.

Answer 1

[SAI SRUJAN]

Hi Nguyen Hoang Hai,

I understand that you are facing an issue in performing the same row operations on different matrices.

You can follow the below given example to resolve the issue.

syms In I1 I2 I3 I4 C1 C2 G1 G2 G3

A = [In - I2;
     -I1;
     -I3;
     -I1;
     -I4;
     -I2];

B = [C1 + 2*G2, 0;
     2*G1, -C2;
     -2*G1 - 2*G2, 0;
     0,C2;
     0, 2*G3;
     0, -2*G3];

m=["A","B"];

for i=1:length(m)
    arr=m(i);
    % performing A(1,:)=A(1,:)-A(6,:);
    text = arr+ "(1,:)="+arr+"(1,:)-"+arr+"(6,:);";
    eval(text);
end

With the help of the above example you can perform same row operations on different matrices.You can use the "eval" function to evaluate a MATLAB expression.For a comprehensive understanding of the "eval" function in MATLAB, please refer to the provided documentation below.

Evaluate MATLAB expression - MATLAB eval - MathWorks India

[Dyuman Joshi]

Nope, this is not a good answer.

DO NOT USE EVAL - https://in.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval#answer_236116

And neither does this answer give the output that OP wants to obtain.