Non polynomial fit: how to proceed?

LPH shared this idea 8 years ago

Answered

Hi Murkle, Hi all,

Extending the conversation of the following thread, I haven’t found a satisfactory solution. My problem is very simple and banal in Physics: I want the student to recover... simply (without CAS) the adjustment values when a model is given.

Let me be more precise. Indeed, in the case of charging a capacitor or a free fall with friction (eg "the fall of Felix Baumgartner"), the phenomenon is modeled by an exponential fit! With GeoGebra , the phenomenon is modeled very easily with :

Fit[list1, a*(1- e^(-b*x))]

Where a and b are initialized sliders. That works very well. :D

The problem is that you can’t recover the "adjusted values of a and b "! :cry: :cry:

Indeed , the commands

Coefficients[ <Polynomial> ] and Coefficients[ <Conic> ]

No longer work...

I just think it hasn't been programmed: are you agree? :confused:

Would it be possible to improve this command? :confused: :confused:

Thank you in advance. :D

Phil

https://ggbm.at/566921

I like this idea

Comments (6)

mathmagic ● 8 years ago

hello

try

b=-f''(0)/f'(0)

a=f'(0)/b

g = TaylorPolynomial[f, 0, 2]

coef = Coefficients[g]

b = -2 (Element[coef, 1] / Element[coef, 2])

a = Element[coef, 2] / b

saludos

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LPH ● 8 years ago

Hi Juan Vicente,

hello

try

b=-f''(0)/f'(0)

a=f'(0)/b

g = TaylorPolynomial[f, 0, 2]

coef = Coefficients[g]

b = -2 (Element[coef, 1] / Element[coef, 2])

a = Element[coef, 2] / b

saludos

Thank you for your answer, but something similar has already been proposed by Noël and in a pedagogical way this solution is not satisfactory to be given to a student. :( :(

I just want the student to use the GeoGebra Coefficients[] tools, already used for other approaches and test the new model. :anguished:

I wanted to know if it is very difficult to improve the Coefficients[] command (very simple in this case)? I think the challenge is to retrieve the values of internal variables that are displayed, no?

Thanks again Juan Vicente for your so quick answer, even if it’s not completely satisfactory.

Phil

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mathmagic ● 8 years ago

hello

OK, i think now i understand you

you need some like this for a general case

i hope developers do it

saludos

you can move the points

https://ggbm.at/566933

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LPH ● 8 years ago

Hi Juan Vicente,

Thank you: that's a nice workaround. :D

hello

OK, i think now i understand you

you need some like this for a general case

i hope developers do it

I hope so. It would be greatfull! :confused:

Cheers,

Phil

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Michael Borcherds ● 8 years ago

Would it be possible to improve this command?

Yes, good idea!

Please try 4.9.265.0

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LPH ● 8 years ago

Hi Murkle,

Please try 4.9.265.0

Thank you very much! It’s OK for me.

It’s a nice improvement for the students.

Thanks for them. :D

Cheers,

Phil

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