Substition of variables in a matrix

Question

Grillteller 2017-2-6

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/323585-substition-of-variables-in-a-matrix

回答： Karan Gill 2017-2-21

Hi,

I have a matrix in the form of

Adiff=
[       Xi1,      Yi1,   Zi1, 1,         0,        0,     0, 0,          -Xi1*xi1,        -Yi1*xi1,    -Zi1*xi1]
[         0,        0,     0, 0,       Xi1,      Yi1,   Zi1, 1,          -Xi1*yi1,        -Yi1*yi1,    -Zi1*yi1]
[       Xi2,      Yi2,   Zi2, 1,         0,        0,     0, 0,          -Xi2*xi2,        -Yi2*xi2,    -Zi2*xi2]
[         0,        0,     0, 0,       Xi2,      Yi2,   Zi2, 1,          -Xi2*yi2,        -Yi2*yi2,    -Zi2*yi2]

Now i want to substitute the symbolic vectors Xi =[Xi1; Xi2 ...] , Yi= [Yi1; Yi2 ...] etc... with vectors with actual values,

e.g.
X1 = -390.93; Y1 = -477.52; Z1 = 0.07;
X2 = -101.5;  Y2 = -479.19; Z2 = 0.11;
Xg = [X1; X2; X3; X4; X5; X6];
Yg = [Y1; Y2; Y3; Y4; Y5; Y6];
Zg = [Z1; Z2; Z3; Z4; Z5; Z6];

I already tried

.
for i=1:1:2
A = subs(Adiff, [Xi(i), Yi(i), Zi(i)], [Xg(i), Yg(i), Zg(i)]);
end

But in this loop, only the second variables will be replaced.

Edit: Additional code pieces

Syms
Xi = sym('Xi',[1,2]); 
Yi = sym('Yi',[1,2]); 
Zi = sym('Zi',[1,2]);

Thanks in advance!

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Answer 1

Karan Gill 2017-2-21

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/323585-substition-of-variables-in-a-matrix#answer_255708

在 MATLAB Online 中打开

This works. Example is below. Can you provide the code for getting Adiff? Are you creating Xi,Yi,Zi first and using them to create Adiff?

>> A = sym('A%d%d',[3 3])
V = A(1,:)
values = randi(100,1,3)
subs(A,V,values)
A =
[ A11, A12, A13]
[ A21, A22, A23]
[ A31, A32, A33]
V =
[ A11, A12, A13]
values =
    15    43    92
ans =
[  15,  43,  92]
[ A21, A22, A23]
[ A31, A32, A33]