How do I solve using centered finite difference formula?

%Boundary conditons

y(0) = 1;

y(5) = 6;

h = 2     %Step size

Centered difference formula;

d2y = (y(i+1) - 2y(i) + y(i-1)) / h^2;

dy = (y(i+1) - y(i-1))/2*h;

    for i = 2:4
      r(i+1) = r(i) + h;
      r(i)*(d2y) + 3*(dy)+10*r(i) = 0
    end

    for i = 1:5
      fprintf('%7.3f   %10.3f \n', r(i), y(i)
    end

I am expecting the program to print the value of y(i). But I can't run the program.

[Philipp Doblhofer]

Hello

Your code has some syntax errors.

Also it seems a bit unclear, what you are trying to do in the first for-loop.

For example this is not allowed in MATLAB. You can't assign a value to a formula

      r(i)*(d2y) + 3*(dy)+10*r(i) = 0

Can you please explain, what you are trying to calculate?

[Mohd Aniq Akmal Maludin]

Hello Phillip,

I am trying to calculate the value of y(2), y(3) and y(4) based on the equation in the for-loop.

[Philipp Doblhofer]

Hello,

maybe this can help you: https://de.mathworks.com/matlabcentral/answers/213823-forward-backward-and-central-differences

You have to do two steps:

1) Calculate dy and d2y for all values of i (1 to 4). The result should be a vector, not a scalar value (like your sample code would suggest)

2) For each i-value you have a system of linear equations. You have to solve them. (y(i) = ...)