how to plot K2 in this differential equation? (v2=1 and u is unit step function)

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성훈 김 2021-8-11

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https://ww2.mathworks.cn/matlabcentral/answers/896177-how-to-plot-k2-in-this-differential-equation-v2-1-and-u-is-unit-step-function

评论： Rhea Chandy 2021-8-25

u is a unit step function and the value of this function is 1 if hr(t) - 0.5 is positive,

otherwise, the value is 0, (Ar=20 and r=5)

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John D'Errico 2021-8-11

编辑：John D'Errico 2021-8-11

K2 is an unknown. It is apparently a coefficient in a differential equation, but that does not tell you anything. What is worse, a differential equation tells you only about the value of a function, here hr as a function of t, but lacking an initial or boundary condition of any kind, it essentially tells you nothing. A differntial equation describes a family of trajectories, but lacking a start or an end point on that trajectory, you can only obtain a (VERY) limited amount of information.

You tell us nothing about the domain this differential equation applies to, so where does t live?

alpha is unknown. No information has been provided about that parameter.

There MAY be a second equation shown, but you show only the lower half of it.

So you have spent a fair amount of time explining what a unit step function is (in two different places), but have told us NO information at all about what anyone would need to know.

At least I assume I know the value of pi. WHEW! A good start there.

Then you ask how to plot the value of an unknown constant?

Let me try the MATLAB crystal ball. Hmm, it tells me nothing that is directly useful to this problem, but it does say you will come into a large sum of money soon.

Walter Roberson 2021-8-12

Is there any relationship between the r that is in r^2, and the r that is the subscript for

and

? I suspect that

might be a function of r (otherwise why mention the r ?) and if it is then you have a partial differential equation rather than an ordinary differential equation.

... Though it is not impossible that you just mean that for each r value, there is a different h function that does not happen to involve r

Rhea Chandy 2021-8-25

Hi,

As the above commenters have already said, the details you've given are not sufficient to help resolve your issue. If you post clearer information, or if you can provide the code you've written to solve the problem and ask a specific question about where you're facing difficulty, we may be able to provide some guidance.

Take a look at this MATLAB Answers post on How to ask a question to help you get answers from the community.

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