# [SciPy-User] scipy.optimize leastsq with numpy longdouble?

Joan Smith joans@MIT....
Wed Nov 17 11:25:32 CST 2010

```Hi,

What do you mean where is the data coming from? It's from an experiment..
function I'm fitting is:
maxwell_boltzmann = lambda v,x: v[0]*(x-C0)**(-4)*np.exp(-(L/v[1])**2*(x-C0)**(-2)) + v[2]

and the data is in an array of longdoubles.
Joan

On Nov 17, 2010, at 12:20 PM, Charles R Harris wrote:

>
>
> On Wed, Nov 17, 2010 at 10:13 AM, Joan Smith <joans@mit.edu> wrote:
> Hi,
>
> I'm fitting a maxwell-botlzmann distribution, using SciPy leastsq. Because of the data I'm fitting, I need high precision (on both the high and low ends), so I'm using numpy.longdouble for my types. Is there a way to use this type with leastsq? As it stands, I'm getting this error:
>
>    v = leastsq(self.chi_squared, self.v_0,  args=self.args, full_output=1)
>  File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/scipy/optimize/minpack.py", line 281, in leastsq
>    maxfev, epsfcn, factor, diag)
> TypeError: array cannot be safely cast to required type
>
> I've been using leastsq for a while, and haven't seen this error before, so I suspect it has to do with using an unusual type.
>
>
> Yep. But where is your data coming from? And how are you trying to do the fit? I suspect that a change of method it the proper way to go here. Josef may have something in the stats model package.
>
> Chuck
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