Matlab help, function handle

[Jackk]

Homework Statement

Hi,

I'm writing a little Matlab function that solves an equation with the help of a function handle.The equation is

x(t) = exp(-a*t)*x0 + exp(-a*t) * int(exp(a*s)*y(s), s=0..t)

I have tried it with two following functions

2. The attempt at a solution

function #1
function ode = ode1sol(a, x0, y, tol)

% if tol is not given
if nargin == 3
tol = 1e-6;
end

t = 0:1:10;

% sub3 being a subfunction
ode = sub3(a,x0,y,t,tol);

function #2
function x = sub3(a,x0,y,t,tol)

f = @(s) exp(a*s) .* y(s);

for i = 1:length(t)
x(i) = exp(-a*t(i))*x0 + exp(-a*t(i)) .* quad(f,0,t(i),tol);
end

--
when I write
t=0:1:10;
ode1sol(1,1,sin(6*t))

Matlab gives me this error
? Subscript indices must either be real positive integers or logicals.

Error in ==> sub3>@(s)exp(a*s).*y(s) at 5
f = @(s) exp(a*s) .* y(s);

Error in ==> quad at 77
y = f(x, varargin{:});

Error in ==> sub3 at 8
x(i) = exp(-a*t(i))*x0 + exp(-a*t(i)) .* quad(f,0,t(i),tol);

Error in ==> ode1sol at 13
ode = sub3(a,x0,y,t,tol);

I'm confusing the indices somehow but I don't know why...

 

[KataKoniK]

Hello,

It looks like you are on the right track with your function. However, there are a few things that could be causing the error you are receiving. Here are a few suggestions to try:

1. Make sure that your input arguments are in the correct order. Based on the code provided, it looks like your function should be called as ode1sol(a, x0, y, tol).

2. Check the dimensions of your input arguments. For example, make sure that the length of t is the same as the length of y.

3. Try using a different integration method instead of quad. For example, you could try using the built-in function trapz or simpson.

4. Make sure that your function handle for y is defined correctly. You may need to use the "arrayfun" function to evaluate y at each value of t.

I hope this helps. Let me know if you are still having trouble and I can try to provide more specific suggestions. Good luck with your function!