How to plot this differential equation

Question

Carlos Castañeda 2018-6-4

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https://ww2.mathworks.cn/matlabcentral/answers/403969-how-to-plot-this-differential-equation

回答： Kim Winter 2018-7-3

Hi guys, I hope you can help me to plot this differential equation:

Y = diff(X,tau); eq = (1-alpha)/(1 - gamma*(Y - Vdr)) + alpha + beta*(Y - Vdr)^2 == F

cond = [X(0) == 0, Y(0) == 0, Vdr == 2, alpha == 0.2, beta == 0, gamma == 3]; sol = dsolve (eq,cond)

Also Y = diff(X,tau) has to be less than Vdr.

I'm completely new using matlab, so I tried to write

fplot(@(tau)sol(tau), [-5 5], '-o')

But I only got a warning message: Function behaves unexpectedly on array inputs. To improve performance, properly vectorize your function to return an output with the same size and shape as the input arguments.

Thanks

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Answer 1

Kim Winter 2018-7-3

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https://ww2.mathworks.cn/matlabcentral/answers/403969-how-to-plot-this-differential-equation#answer_327324

Hi, You have "tau" as an input, but never initialize it before the @fplot. For example, if you try to run just line 1 (Y=diff(X,tau);), you will get the error that X is uninitialized (although tau is not either). If you initialize your inputs, you may have a better result!

-Kim