How to plot a function with an unknown answer and a changing variable?

Question

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Say I have an equation with a changing variable, call it R. I want to have the values of R between 0.001 and 0.01.

R is a part of an equation X, and I want to plot the value of X for the changing variables of R. How do I do this?

I tried to use fplot, but it was only giving me a straight line, which I know is not the answer.

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Walter Roberson 2018-2-8

One of the most common reasons for getting an unexpected straight line is if you have used / in a place you need ./ instead .

But beyond that, we would need to see code.

Nicole Cronin 2018-2-8

编辑：Walter Roberson 2018-2-8

Here's the code I wrote -

fplot(@( R ) X ,[0.001 0.010]

for the equation

X = (1/sqrt( R )) + 2.0*log((m/(3.7*D))+ (2.51/(Re*sqrt( R ))));

m, D, and Re are variables I currently have saved.

Answer 1

Walter Roberson 2018-2-8

0 个投票

   X = @(R) (1/sqrt( R )) + 2.0*log((m/(3.7*D))+ (2.51/(Re*sqrt( R ))));
   fplot(X, [0.001 0.010])