Need help to form equations

Question

Sameer 2014-6-6

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/132662-need-help-to-form-equations

编辑： Sameer 2014-6-6

Hello all

I want to form the equations through the matlab commands,I have the matrix of constants....Can anyone guide how can I form the equations. Example equations

1) a1v1^2-a2v2-a3v3^2-a4v4=0

2) a3v3^2-a4v4-a1v1=0

3) a1v1+a4v4-a3v3^2=0

4) a2v2+a1v1+a3v3-a4v4=0

where a's are constant and I have a matrix for a and I have to find v's.

I want to use them in fsolve.

please guide!!!

Regards

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Answer 1

David Sanchez 2014-6-6

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/132662-need-help-to-form-equations#answer_139625

在 MATLAB Online 中打开

a = rand(1,4); % your a matrix
syms v1 v2 v3 v4
S = solve( a(1)*v1^2-a(2)*v2-a(3)*v3^2-a(4)*v4==0,...
 a(3)*v3^2-a(4)*v4-a(1)*v1==0,...
 a(1)*v1+a(4)*v4-a(3)*v3^2==0,...
 a(2)*v2+a(1)*v1+a(3)*v3-a(4)*v4==0)
S = 
      v1: [4x1 sym]
      v2: [4x1 sym]
      v3: [4x1 sym]
      v4: [4x1 sym]

To display the solutions, access the elements of the structure array S

S.v1
ans =
                                                                             0
                                            0.76082746713182598996024745838092
   - 0.38041373356591299498012372919046 - 0.65889591443313132581875790778993*i
   - 0.38041373356591299498012372919046 + 0.65889591443313132581875790778993*i

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Sameer 2014-6-6

Hello...thanks for replying but my concern is that i have plenty of equations,thus i want to generate the equations using a loop,therefore i want to know how can I acheive that...

Awaiting a response

Regards

Sameer 2014-6-6

在 MATLAB Online 中打开

To give the more clear idea:

function F = Equation_trial( x )

F= [50-20*x(1)-30*x(2)-40*x(3);

    30*x(2)-50*x(4)-60*x(5);   
    20*x(1)+60*x(5)-70*x(6);    
    70*x(6)+50*x(4)+40*x(3)-80*x(7);   
    50000+20-x(8)-500*x(1)^2;   
    50000+20-x(9)-500*x(2)^2;    
    50000+20-x(10)-500*x(3)^2;  
    500*x(2)^2+x(9)-x(11)-500*x(4)^2;    
    500*x(2)^2+x(9)-x(12)-500*x(5)^2;    
    500*x(6)^2+x(13)-x(8)-500*x(1)^2;  
    500*x(6)^2+x(13)-x(12)-500*x(5)^2;   
    500*x(7)^2+x(14)-x(10)-500*x(3)^2;  
    500*x(7)^2+x(14)-x(11)-500*x(4)^2; 
    500*x(7)^2+x(14)-x(13)-500*x(6)^2];