[SciPy-User] bug in optimize.curve_fit ?

Oleksandr Huziy guziy.sasha@gmail....
Thu Aug 4 09:26:23 CDT 2011


Hi,

if you did x = list(x) it becomes a simple list, which cannot be multiplied
by a number.
don't do this.

--
Oleksandr Huziy


2011/8/4 Xavier Gnata <xavier.gnata@gmail.com>

> Hi,
>
> def func(x, a, b, c):
>    return a*np.exp(-b*x) + c
> x = np.linspace(0,4,50)
> y = func(x, 2.5, 1.3, 0.5)
> yn = y + 0.2*np.random.normal(size=len(x))
> popt, pcov = curve_fit(func,x, yn)
>
> works vey well but if you change it to:
>
> def func(x, a, b, c):
>    return a*np.exp(-b*x) + c
> x = list(np.linspace(0,4,50))
> y = func(x, 2.5, 1.3, 0.5)
> yn = y + 0.2*np.random.normal(size=len(x))
> popt, pcov = curve_fit(func, x, yn)
>
> then x is a list and we get this error:
> "TypeError: can't multiply sequence by non-int of type 'float'"
>
> However, according to the documentation, xdata : An N-length sequence
> or an (k,N)-shaped array. I understand this statement as : "either a
> list, a tuple or an array". Should optimize.curve_fit internally cast
> xdata to an array? I would think so.
>
>
>
> Xavier
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