while loop not doing what i want?

e   =0.0015;
D   =50;
V   =2;
Dm  =0.05;
v   =1.01*10^-6;
Re  = V*Dm/v;
N   =1000;
f   = linspace(0.008,0.1,N);

i   = 0;
f_abs = 1;
FF = 0.008;

while FF(end) < f_abs;
    i = i + 1;
    FF = log(e/D/3.7 + 2.51*Re*sqrt (f(i)))*sqrt(f(i))*-2;
end

Trying to iterate through f until FF is equal to 1 or within a range of 0.001 form 1 in this case its f_abs. Please keep explanation simple as i am a new user with no programming knowledge

Thank you in advance James

[EDITED, Jan, Please apply a proper code formatting - thanks]

[Jan]

You forgot to ask a question. It is not clearly explain what you want. We see the code, we see what the code does, but we cannot know, what you expect instead.

"FF(end)" looks like you want to store the results in a vector. But the code overwrite the scalar FF in each iteration.

Answer 1

[A Jenkins]

Your FF never approaches 1. Perhaps you have an error in your function?

Answer 2

[Jan]

What about:

FF         = -2 * log(e/D/3.7 + 2.51 * Re * sqrt(f)) * sqrt(f);
firstmatch = find(FF >= f_abs - 0.001, 1);
FF(firstmatch)