I have a function and I would like for it to print out an answer if I feed it a value.

2 次查看（过去 30 天）
Peter Phung
Peter Phung 2018-5-4
回答： Star Strider 2018-5-4
I am using the Colebrook equation, which is a function of "f" and "Re" PLEASE READ(RE IS WHERE 126,400 IS). I haven't used MATLAB in a long time. Basically if I plug in a value for f into the equation, I get a value for Re. I need to do this for f = 0:0.0001:1 (which is a 10000x1 double) so I'll get the respective values for Re with respect to f = 0:0.0001:1. How do I go about doing this in MATLAB? I understand that I need to set the equation equal to zero, but I do not know what to do after that.
Here is the equation

请先登录，再回答此问题。

采纳的回答

Star Strider
Star Strider 2018-5-4
Probably the easiest way is to have the Symbolic Math Toolbox solve for ‘Re’, then do the calculations in an anonymous function created by matlabFunction:
syms f Re
Eqn = 1/sqrt(f) == -2*log(4.2E-5/3.7 + 2.51/(Re*sqrt(f)));
Re_sol = solve(Eqn, Re);
ReFcn = matlabFunction(Re_sol)
f = linspace(0, 1, 1E+4);
figure
semilogy(f, ReFcn(f))
grid
xlabel('f')
ylabel('Re')
This produces:
ReFcn = @(f) (1.0./sqrt(f).*(2.51e2./1.0e2))./(exp(1.0./sqrt(f).*(-1.0./2.0))-1.135135135135135e-5);
You might want to use abs(ReFcn(f) in the plot, to avoid the ‘Warning: Negative data ignored’ message.

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 Special Values 的更多信息

标签

Community Treasure Hunt

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

Start Hunting!

Translated by