Re: [Matplotlib-users] How to plot Chebyshev polynolmials

[Daniel H. <dh...@gm...>]

I think that you're misusing Chebyshev (do you really only want to give "3"
as a coefficient..which is just the constant function 3), and you have to
evaluate it in order to give matplotlib some x and y data to plot.

from matplotlib import pyplot as plt
import numpy as np

x = np.linspace(-1.0,1.0)
test = np.polynomial.Chebyshev((1,2,3))
y = test(x)
plt.plot(x,y)
plt.show()



On Tue, Jan 10, 2012 at 9:10 AM, Fabien Lafont <laf...@gm...>wrote:

> I'm trying to plot Chebyshev polynolmials using:
> numpy.polynomial.Chebyshev:
>
>
> import math
> from numpy import *
> from numpy import polynomial as pol
> from pylab import *
> from scipy import *
> from scipy import optimize
> import warnings
> warnings.simplefilter('ignore', np.RankWarning)
>
>
> test = pol.Chebyshev(3)
> print test
> plot (test)
>
>
> show()
> =======================================================================
>
> The print return:      cheb([ 3.])
>
> =======================================================================
> and plot :
>
>
> Traceback (most recent call last):
>  File "T:\Dropbox\Thèse\Python\fit sonde\test_poly_Tcheb.py", line
> 32, in <module>
>    plot (test)
>  File "C:\Python27\lib\site-packages\matplotlib\pyplot.py", line 2458, in
> plot
>    ret = ax.plot(*args, **kwargs)
>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 3849, in
> plot
>    self.add_line(line)
>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1443,
> in add_line
>    self._update_line_limits(line)
>  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1451,
> in _update_line_limits
>    p = line.get_path()
>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 644,
> in get_path
>    self.recache()
>  File "C:\Python27\lib\site-packages\matplotlib\lines.py", line 401, in
> recache
>    y = np.asarray(yconv, np.float_)
>  File "C:\Python27\lib\site-packages\numpy\core\numeric.py", line
> 235, in asarray
>    return array(a, dtype, copy=False, order=order)
> TypeError: float() argument must be a string or a number
>
>
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-- 
Daniel Hyams
dh...@gm...