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

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

[Dyuman Joshi]

It's quite simple, you just have to separate the terms and get the coefficients.

1st eq

A=[m1 0 c1+c2 -c2 k1+k2 -k2], B=0;

2nd eq

A=[0 m2 -c2 c2 -k2 k2], B=0;

[Rahul Jangid]

hi thanks for replying

but actually i want to do this automatically so that i can make three different matrices [mass], [Damping] & [Stiffness]

for this i need to first extract coffecient matrix automatically

my actual system of equation is a bit complex and there are 14 variables .

it will be a great if u can help me in this .

[Dyuman Joshi]

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]

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

Answer 1

[Mann Baidi]

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!

Answer 2

[Walter Roberson]

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()