Array indices must be positive integers or logical values Error

1 view (last 30 days)
The question I am trying to answer is: Write a program to test the two finite difference approximations in section 1.6 (the forward and centered difference formulas). Test your program on the function arctan(x) at x=sqrt(2).Start with h = 1/2, and generate a sequence of approximations by reducing h by a factor of 2 each time, until h = 2−40. Observe how the error changes with h.
So far I have;
x=sqrt(2) ;
%Forward Euler
I keep getting the array indices must be positive integers or logical values error.
Abigail Mullen
Abigail Mullen on 4 Sep 2018
I suppose I am just not sure how to do this problem, thank you for your help - I am new to matlab.

Sign in to comment.

Answers (1)

Ashutosh Prasad
Ashutosh Prasad on 7 Sep 2018
The error that you are getting is because of the way you are defining the h vector. Your definition creates an empty vector with no elements. But I understand you want h to be halved on each iteration, that's when loops come handy.
Try execution the following script
f = @(x) atan(x);
x = sqrt(2) ;
h = 0.5;
%Forward Euler
while(h >= 2^(-40))
F = ((f(x+h)-f(x))/h);
h = h/2;
Let me know if this helps

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by