How to parse a Matrix ODE45. Getting simulation error

Hi Dears!

I am simulating a set of Ordinary Differntial Equations ODEs using ODE45 solver. I need to parse a matrix (i.e. zeta=rand(46,16)) into the ODE45, however I am getting this error:

Unable to perform assignment because the left and right sides have a different number of elements.

Error in OscillatorExample_V2>LinearOscillatorFree (line 26)

y(2)=(-2*zeta*y(2))-(w*y(1));

Error in odearguments (line 90)

f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ode45 (line 115)

odearguments(FcnHandlesUsed, solver_name, ode, tspan, y0, options, varargin);

Error in OscillatorExample_V2 (line 9)

[T, Y] = ode45(@LinearOscillatorFree, tspan, initcond, [],zeta);

Can you please help me with this to get the right results? Many thanks in advance!

close all; clear all; clc;

zeta=rand(46,16);
tspan=[0 4700];
initcond= [0 1];

for n = 1:length(zeta)
[T, Y] = ode45(@LinearOscillatorFree, tspan, initcond, [],zeta);
figure(1);
plot(T, Y(:,1));
hold on
end


m= length(Y);
for i=1:m
y(i,:)=feval('LinearOscillatorFree',T(i),Y(i,:),zeta);
end
y=y';


function dy = LinearOscillatorFree(t, y,zeta)
w=0.5;
y(1)=y(2);
y(2)=(-2*zeta*y(2))-(w*y(1));
dy= [y(1); y(2)];
end

[James Tursa]

What is the ODE you are trying to solve, and what is the purpose of zeta?

[Shy]

The used ODE is ode45, and the purpose of zeta is a matrix which is parsed into the (LinearOscillatorFree) function I used in my code.

[James Tursa]

I mean, what is the differential equation you are trying to solve? Post the equation for us to see, with a definition of zeta. Are you trying to run a Monte-Carlo simulation with various random values of zeta?

[Shy]

Hi James,

This is my code with the definition of zeta and the differential equations: (Yes I am using a Monte-Carlo simulation)

close all; clear all; clc;

zeta=rand(46,16);

tspan=[0 4700];

initcond= [0 1];

for n = 1:length(zeta)

[T, Y] = ode45(@LinearOscillatorFree, tspan, initcond, [],zeta);

figure(1);

plot(T, Y(:,1));

hold on

end

m= length(Y);

for i=1:m

y(i,:)=feval('LinearOscillatorFree',T(i),Y(i,:),zeta);

end

y=y';

function dy = LinearOscillatorFree(t, y,zeta)

w=0.5;

y(1)=y(2);

y(2)=(-2*zeta*y(2))-(w*y(1));

dy= [y(1); y(2)];

end

[Shy]

These are the differential equations:

[James Tursa]

Your equations don't make sense to me. How can y1 and y2 be scalars and yet zeta be a matrix? The dimensions of the equations don't match. It might make sense for zeta fo be a scalar that is randomly selected from a distribution, and then run Monte-Carlo on that. But what you have written doesn't make sense. Where did these equations come from? Why the 46x16 size of zeta?

[Shy]

I am running a similar system like that consisting of four ODEs, so the question is how to parse a matrix into the ode45 solver? Can you please provide me with your email so that I can email you on?