Why is my integration in Mathematica not working?

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Discussion Overview

The discussion revolves around issues related to fitting experimental data using Mathematica and MATLAB, specifically focusing on integration problems and the use of coupled equations in fitting parameters. Participants seek advice on how to implement their equations in these software tools.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant describes a fitting problem in Mathematica involving a function dependent on temperature and a coupled equation for Y, seeking advice on obtaining a parameter u.
  • Another participant presents a fitting problem in MATLAB, involving a different equation with parameters a, u, and g, and asks if MATLAB can handle the iterative solution of the coupled equations.
  • A suggestion is made that Mathematica's FindFit function could be useful for the fitting process.
  • One participant expresses confusion about an integration issue in Mathematica involving the HeavisideTheta function, asking for help.
  • Another participant claims the integration works for them and suggests a possible typo in the original query, later noting that the expected answer should be 0.1, indicating a potential bug in the integration process.

Areas of Agreement / Disagreement

Participants express differing views on the integration issue, with some suggesting it works correctly while others believe there may be a bug. The fitting problems in Mathematica and MATLAB remain unresolved, with no consensus on the best approach.

Contextual Notes

Participants mention the need for solving coupled equations and the dependency of parameters on the system, which may complicate the fitting process. There is also uncertainty regarding the integration results in Mathematica.

aminbkh
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Hi,
I have a question about fitting in Mathematica.I have a function like this:
F=T*Y^(0.5) T is temperature but Y obtained from this coupled equation 1-u*Y=u(1-u/Y^.4)^.5*Y
I have T and F from experimental data.so I want to obtain u from fitting.
could you please advise me how can I do it by Mathematica.
Thank you
 
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Question about matlab

Hi,
I have question if you could answer me, I really appreciate it. I have an equation which I wan to solve it to experimental data \[Rho] = t*Y^.5*a + Y^.8/sqrt (1 + 4*Y)*t*a^2 where a is parameter which I want to obtain by fitting and t is vector that I know for each experiment. and Y obey this equation 1 - (1 - u)*Y = u*(1 + g/t*y^.5)^.5*Y^.43 where u and g are again system dependent parameter which should be obtained by fitting it means that in each iteration first that coupled equation should be solved with respect to Y and put in rho equation to obtain u,g and a do you know if MATLAB is able to do that or not?or ant other suggestion I really appreciate your help
 


thank you for your answer
but the problem is the function Y should be solved and then put in second equation and both of them have some adujstable parameters,
could you advise me more please.
 


Hi all,
I have this integration in mathematica but I don't know why doest work.
Could you please help me?

Integrate[HeavisideTheta[0.1 - x], {x, 0, 100}]

Thank you so much for your help
 


aminbkh said:
Hi all,
I have this integration in mathematica but I don't know why doest work.
Could you please help me?

Integrate[HeavisideTheta[0.1 - x], {x, 0, 100}]

Thank you so much for your help

It works when I do it. See the attached notebook. Did you mis-type it?

Edit: Oops, I see what you mean. The answer should be 0.1, not 100.0. Looks like a bug. It plots the Heviside function correctly, but appears not to integrate it correctly. Hmmm.
 

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