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while loop not doing what i want?

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Jimmy Jeenjiu
Jimmy Jeenjiu 2013-9-12
关闭： MATLAB Answer Bot 2021-8-20
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]
  1 个评论
Jan
Jan 2013-9-12
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.

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回答（2 个）

A Jenkins
A Jenkins 2013-9-12
Your FF never approaches 1. Perhaps you have an error in your function?
Jan
Jan 2013-9-12
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)

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