# How to plot Chebyshev polynolmials

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
File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1443,
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

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 <lafont.fabien@…287…> 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

``````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,

``````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
dhyams@…287…

No I just want to plot the third Shebitchev polynomial.

2012/1/10 Daniel Hyams <dhyams@...287...>:

···

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 <lafont.fabien@...287...> > 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
File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 1443,
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

------------------------------------------------------------------------------
Write once. Port to many.
Get the SDK and tools to simplify cross-platform app development. Create
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http://p.sf.net/sfu/intel-appdev
_______________________________________________
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--
Daniel Hyams
dhyams@...287...

------------------------------------------------------------------------------
Write once. Port to many.
Get the SDK and tools to simplify cross-platform app development. Create
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http://p.sf.net/sfu/intel-appdev
_______________________________________________
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Regardless of exactly which polynomial you are after, I’ve showed you how to plot a cheb. poly. Can you not work with the code given and plot the exact variation of polynomial you want?

···

On Tue, Jan 10, 2012 at 9:46 AM, Fabien Lafont <lafont.fabien@…287…> wrote:

No I just want to plot the third Shebitchev polynomial.

2012/1/10 Daniel Hyams <dhyams@…1003…7…>:

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 <lafont.fabien@…287…> > > > 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

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

File “C:\Python27\lib\site-packages\matplotlib\axes.py”, line 1443,

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

Write once. Port to many.

Get the SDK and tools to simplify cross-platform app development. Create

new or port existing apps to sell to consumers worldwide. Explore the

Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join

http://p.sf.net/sfu/intel-appdev

Matplotlib-users mailing list

Matplotlib-users@lists.sourceforge.net

https://lists.sourceforge.net/lists/listinfo/matplotlib-users

Daniel Hyams

dhyams@…287…

Write once. Port to many.

Get the SDK and tools to simplify cross-platform app development. Create

new or port existing apps to sell to consumers worldwide. Explore the

Intel AppUpSM program developer opportunity. appdeveloper.intel.com/join

http://p.sf.net/sfu/intel-appdev

Matplotlib-users mailing list

Matplotlib-users@lists.sourceforge.net

https://lists.sourceforge.net/lists/listinfo/matplotlib-users

Daniel Hyams
dhyams@…287…