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Asked by Dushyant
on 15 Sep 2013

I need some guidance regarding numerical ordinary differential equation

I have nine simultaneous first order differential (OD) equations which can be combinedly written as: dY/dt = A*Y + b where Y is a vector consisting of 9 terms and A is a matrix of size 9,3.

Can someone suggest me how should I start?

The paper that, I am looking at, briefly explains the procedure as: “The problem can be analytically without further simplification with the use of Matlab built-in function of matrix left division (\) and matrix power (expm 1) “ Regards, DK

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Answer by Azzi Abdelmalek
on 15 Sep 2013

A should be a 9x9 array

write and save this function as myeq.m

function dY=myeq(t,Y) A=randi(9,9,9) ; % Example b=1; dY=zeros(9,1) ; dY = A*Y + b;

Then call it

y0=zeros(9,1)% Initial conditions tspan=[0 10]; [t,y]=ode45(@myeq2,tspan,y0)

Azzi Abdelmalek
on 16 Sep 2013

**[ Dushyant commented]**

Thanks.

Sorry, I mistakenly wrote wrong dimension for A.

Regards, Dushyant

## 1 Comment

## Azzi Abdelmalek

Direct link to this comment:http://www.mathworks.com/matlabcentral/answers/87258#comment_169061

If Y is 9x1 array and A is 9x3 array, how can you do A*Y ?