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wanna creat a matrix of unknowns and write some equations with those unknowns and then take the matrix of coefficients

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Aref Mirjalili 2021-1-11

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评论： Walter Roberson 2021-1-12

I want to creat a matrix of unknowns like below

t(1,1) t(1,2)

t(2,1) t(2,2)

then i want to write some equations with this like

2*t(1,1) + 3*t(1,2)

then take the matrix of coefficients : a=[2 3]

I tried syms t(i,j) but it cant be done like this

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回答（2 个）

David Hill 2021-1-11

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syms a b c d;
t=[a b;c d];
coef=[2 3];
eqn=dot(coef,t(1,:));

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Aref Mirjalili 2021-1-11

actually the matrix i wanna use is 15by15 and with 15unknowns

i would like it in form i mentioned before

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Walter Roberson 2021-1-11

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t = sym('t%d_%d',[15,15]);

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Aref Mirjalili 2021-1-12

在 MATLAB Online 中打开

thanks but my next question is

i have a code like this:

for i=1:15
    for j=1:15
        t(i+1,j)+t(i,j+1)+t(i-1,j)+t(i,j-1)-4*t(i,j)
    end
end

i want the matrix of coefficients of t

and it will be like this:

Walter Roberson 2021-1-12

Add a number of diag() ?

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