Having trouble implementing a function

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.

[Chris]

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?

Answer 1

[sixwwwwww]

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