Hi all! I'm working with the function find_fit and now I need to fit a piecewise function, but I have tried it returns errors. How could I fit a picewise function?
Thanks
According to the documentation of find_fit, the "model" can be a plain python function:
model Either a symbolic expression, symbolic function, or a Python function. model has to be a function of the variables (x1;x2;:::;xk) and free parameters (a1;a2;:::;al).
and nothing stops you from using conditionals inside f:
def f(t,a) :
if t<1/2:
return t*a
return (1-t)*a
data = [(i,i*(1-i)) for i in xsrange(0, 1, 0.1)]
var('a, x')
d = find_fit(data,f, parameters=[a], variables=[x], solution_dict=True)
a0 = d[a]
print a0
point(data) + plot(lambda t:f(t,a0), 0,1)yes that is true, but i think conditional statement is slower.
If it is slower than Piecewise, I'd say that's only because of fast_callable. But you can also compile the function f with cython
Asked: 13 years ago
Seen: 986 times
Last updated: Jan 17 '12
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Yes. It turns out that piecewise does not have a member function variables. So len(variables) retruns a error. Is there a ticket about this? I could not find any. If the function happens to be piecewise we should call length and not len(variables)
Sounds like you should open a ticket for this :)
A ticket has been created (http://trac.sagemath.org/sage_trac/ticket/12316). I will try to fix it soon.
Ok, thank you.