Having trouble implementing a function

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Chris
Chris on 22 Oct 2013
Answered: sixwwwwww on 22 Oct 2013
I have this function following eulers theorem and its all nicely labeled but i cant make it work because it keeps saying unknown operator. it says to put the function as an inline function and then graph euler.m i am very lost as to how to make this work.
in one file i have
f=inline('-2*y')
and in another file i have eulers
function [t,y] = euler(f,tspan,y0,N);
% Solves the IVP y' = f(t,y), y(t0) = y0 in the time interval tspan = [t0,tf]
% using Euler's method with N time steps.
% Input:
% f = name of inline function or function M-file that evaluates the ODE
% (if not an inline function, use: euler(@f,tspan,y0,N))
% For a system, the f must be given as column vector.
% tspan = [t0, tf] where t0 = initial time value and tf = final time value
% y0 = initial value of the dependent variable. If solving a system,
% initial conditions must be given as a vector.
% N = number of steps used.
% Output:
% t = vector of time values where the solution was computed
% y = vector of computed solution values.
m = length(-30);
t0 = 0;
tf = 10;
h = (tf-t0)/N; % evaluate the time step size
t = linspace(t0,tf,N+1); % create the vector of t values
y = zeros(m,N+1); % allocate memory for the output y
y(:,1) = y0'; % set initial condition
for n=1:N
y(:,n+1) = y(:,n) + h*f(t(n),y(:,n)); % implement Euler's method
end
t = t'; y = y'; % change t and y from row to column vectors
end
I keep trying to input -2*y for my f and [0,10] for my tspan and all the other constants in the function but it is not working.
  1 Comment
Chris
Chris on 22 Oct 2013
update. I think i almost have it figured out. i have them both on the same file defining and inline function and the i just called eulers but now its telling me not enough inputs for my inline function. what does it mean?

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Accepted Answer

sixwwwwww
sixwwwwww on 22 Oct 2013
It means you should input all four values for "f,tspan,y0,N" because your "euler" function has four inputs

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