My Mathlab code is giving me a wrong answer, and I don't know why.

I'm trying to write a script to use Euler's method to solve ODE's. In line 10, I'm running into issues. On the second iteration, my code is telling me that 2 + 1 * 2 = 3.

I should clarify that I'm just using the problem off of the Euler's Method wikipedia page in which:

y' = y

y(0) = 1

Here's my code:

iterations = 4;
initial = [0,1];
step_size = 1;
f = @(x) initial(2);
while iterations > 0
  initial(2) = initial(2) + step_size * f(initial(1));
  initial(1) = initial(1) + step_size;
  iterations = iterations - 1;
end
%Report Answer
initial(2)

Answer 1

[OCDER]

Move the function handle f inside the while loop. The moment a function handle is created, it uses all constants at the CURRENT state the function handle was generated. The variable initial, when the function handle was generated, is [0 1] and is never updated in the loop. This fixes the issue:

iterations = 4;
initial = [0,1];
step_size = 1;
while iterations > 0
  f = @(x) initial(2);
  initial(2) = initial(2) + step_size * f(initial(1)); %Same as: initial(2) + step_size*initial(2)
  initial(1) = initial(1) + step_size;
  iterations = iterations - 1;
end

[Ken]

I was not aware of that. Thank you sir.

[OCDER]

You're welcome!