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# Use assume() on find_fit Hi everyone,

does anyone know how I can use assumptions with find_fit? A minimal example would be

var('a,b,x')
assume(a>0,b>0)
find_fit([(2,2),(3,2.9),(4,4.1)],(a+1)/b*x,variables=[x],initial_guess=(-2,-2))


and the output is

[a == -105.66654155674746, b == -104.30685450333799]


Any help or hint on where to find a solution is appriciated. Thanks in advance.

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## Comments

Considering that find_fit uses Scipy and assumptions are in Maxima, I think it's quite unlikely that this would do much. I guess we could try to run them through assumptions, though this might slow it down appreciably.

## 1 Answer

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You could fake it like this:

find_fit([(2,2),(3,2.9),(4,4.1)],(abs(a)+1)/abs(b)*x,variables=[x],initial_guess=(-2,-2))


So the best fit values of a,b are negative, but their absolute values are a "good fit" in your model.

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## Stats

Asked: 2012-06-21 16:24:13 +0200

Seen: 225 times

Last updated: Jun 23 '12