I want to convert few equations into matrix form >>>>>>

Question

Rahul Jangid 2022-11-24

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回答： Walter Roberson 2023-9-10

Can some one help me to convert those equations into matrix form

Where the form of matrix is as A*X = B where X = [diff(x1(t), t, t); diff(x2(t), t, t); x1d; x2d; x1; x2]

the equations are as shown below:

m1*diff(x1(t), t, t) + c1*x1d + k1*x1 + (c2*(2*x1d - 2*x2d))/2 + (k2*(2*x1 - 2*x2))/2 == 0

m2*diff(x2(t), t, t) - (c2*(2*x1d - 2*x2d))/2 - (k2*(2*x1 - 2*x2))/2 == 0

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Dyuman Joshi 2022-11-25

编辑：Dyuman Joshi 2022-11-25

Automatically? Meaning with a code?

You can use collect. Other than that, I think it's highly unlikely you can do it 'automatically'

Rahul Jangid 2022-11-28

yeah i want to do it using code bcz the actual problem i am solving have very complex and around 12 variables.

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Answer 1

Mann Baidi 2023-9-10

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Hi Rahul,

I understand you would like to convert variable equation into a matrix form. Currently, MathWorks don’t have a function for this. You would have to make the matrix manually. For more information, you can refer to the following answer.

https://in.mathworks.com/matlabcentral/answers/1862683-how-to-convert-pde-into-matrix-form#answer_1111773

Thanks!

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Answer 2

Walter Roberson 2023-9-10

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I recommend that you examine the work-flow of the first example of odeFunction as that shows converting orders and gathering terms and building mass matrix, and generating anonymous functions for use with routines such as ode45()