Simpson's Method for Computing Relative Error of x

[chronicals]

I want to compute x within 0.1% relative error with Simpson method, these are my m-files. Which command i should add for this?

function simps(a, b, n)
%simps(a, b, n) approximates the integral of a function f(x) in the
%interval [a;b] by the composite simpson rule
%n is the number of subintervals

h = (b-a)/n;

sum_even = 0;

for i = 1:n/2-1
x(i) = a + 2*i*h;
sum_even = sum_even + f(x(i));
end

sum_odd = 0;

for i = 1:n/2
x(i) = a + (2*i-1)*h;
sum_odd = sum_odd + f(x(i));
end

integral = h*(f(a)+ 2*sum_even + 4*sum_odd +f(b))/3function y = f(x)
y=1/x;

 

[DrClaude]

The best way to get an error estimate is to do the integration with two different values of the step (say h and h/2) and use the relative difference between the two results.