Hello,
On Sat, Jan 10, 2009 at 8:29 PM, slybro <[email protected]> wrote:
>
> I am having trouble using the polyfit function. Here are the
> commands:
>
> import numpy as np
> import scipy as sc
>
> vp = np.array([1.0, 5.0, 10.0, 20.0, 40.0, 60.0, 100.0, 200.0, 400.0,
> 760.0])
>
> T = np.array([-36.7, -19.6, -11.5, -2.6, 7.6, 15.4, 26.1, 42.2, 60.6,
> 80.1])
>
> (a,b,c,d) = np.polyfit(vp,T,3)
You must explicitly make the Numpy array's have dtype float as numpy
does not automatically convert Sage's RealNumber to a float. If you
don't do this, the array's dtype will be "object'.
sage: vp = np.array([1.0, 5.0, 10.0, 20.0, 40.0, 60.0, 100.0, 200.0,
400.0, 760.0],dtype=float)
sage: T = np.array([-36.7, -19.6, -11.5, -2.6, 7.6, 15.4, 26.1, 42.2,
60.6, 80.1], dtype=float)
sage: np.polyfit(vp,T,3)
array([ 1.13148994e-06, -1.49004659e-03, 6.12784745e-01,
-2.13934587e+01])
There are other ways to achieve a similar effect such as turning off
the Sage preparser with "preparser(False)" or making Sage's RealNumber
an alias of float ("RealNumber = float").
--Mike
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