Not able to stop value of iterations

This is my code. I get my x value correctly, and stops there. The if condition is not iterating and I'm not able to find the root or the number of iterations.

Can anybody please clear me about this?

function [x,i]=newton(R,f,Re,x0,maxiter,tol)

for i=1:maxiter

x=x0-(colebrook(R,f,Re)/colebrook_deriv(R,f,Re))

if (x-x0)<tol

break

disp(['root= ',num2str(x)])

end

fprintf('The number of iterations is: %d\n',i)

end

Answer 1

[VBBV]

%if true
 function 
 ...
 end

Add a missing end to close function

[Nilaa Maragathavelan]

yeah tried that...still not helping. the code iterates for the given number of iterations without stopping

[VBBV]

%if true
function [x]=newton(R,f,Re,x0,maxiter,tol)

Try without the iteration index i as the function output

[VBBV]

Try to check if the two functions that are being called

(colebrook(R,f,Re)/colebrook_deriv(R,f,Re))

Have any indefinite criteria inside them. The other way is to increase the tolerance so that it enters if condition

Answer 2

[Alan Stevens]

Better as something like

tol = 10^-8;       % or whatever you desire
maxiter = 100;     %    ditto
err = 1;
its = 0;
while err>tol && its<maxiter
    x=x0-(colebrook(R,f,Re)/colebrook_deriv(R,f,Re));
    err = abs(x-x0);
    x0 = x;
    its = its+1;
end
disp(['root= ',num2str(x)])
fprintf('The number of iterations is: %d\n',its)

and, come to think of it, shouldn't colebrook and colebrook_deriv be functions of x, or, alternatively, shouldn't x and x0 be f and f0?