# Fit with Chebyshev Polynomials

I have a basic problem (I think)

I try to fit some data with this function
http://docs.scipy.org/doc/numpy/reference/generated/numpy.polynomial.Chebyshev.fit.html

But it return an error:

fit = chebyshev.fit(T,R,3)
NameError: name 'chebyshev' is not defined

I don't understand I've imported Numpy and polynomials... An Idea?

import math
from numpy import *
from numpy import polynomial
from pylab import *
from scipy import *
from scipy import optimize
import warnings
warnings.simplefilter('ignore', np.RankWarning)

R = [ 9011.5 , 7822.7 , 6253.9 , 4877.56 , 3892.08 ,
3221.41 , 2647.05,
2260.94 , 1959.72 , 1712.06 , 1522.28 , 1367.87 , 1242.953
, 1185.092,
1104.452 , 1031.862 , 919.8644 , 832.9942 , 767.8944 , 715.1569,
671.6301 , 635.1634 , 604.284 , 577.5536]

T = range(0,len(R))
plot (T,R,".")
show()
fit = chebyshev.fit(T,R,3)
print fit

The function would be in the “polynomial” namespace. So “polynomial.chebyshev()” would work. To reduce typing, you can import a module “as” some other name.

from numpy import polynomial as poly

fit = poly.chebyshev.fit(T,R,3)

Importing modules is very flexible and I suggest reading up on it.

Ben Root

···

On Wednesday, December 14, 2011, Fabien Lafont <lafont.fabien@…287…> wrote:

I have a basic problem (I think)

I try to fit some data with this function

http://docs.scipy.org/doc/numpy/reference/generated/numpy.polynomial.Chebyshev.fit.html

But it return an error:

fit = chebyshev.fit(T,R,3)
NameError: name ‘chebyshev’ is not defined

I don’t understand I’ve imported Numpy and polynomials… An Idea?

import math

from numpy import *
from numpy import polynomial
from pylab import *
from scipy import *
from scipy import optimize
import warnings
warnings.simplefilter(‘ignore’, np.RankWarning)

R = [ 9011.5 , 7822.7 , 6253.9 , 4877.56 , 3892.08 ,
3221.41 , 2647.05,
2260.94 , 1959.72 , 1712.06 , 1522.28 , 1367.87 , 1242.953
, 1185.092,
1104.452 , 1031.862 , 919.8644 , 832.9942 , 767.8944 , 715.1569,

671.6301 , 635.1634 , 604.284 , 577.5536]

T = range(0,len®)
plot (T,R,".")
show()
fit = chebyshev.fit(T,R,3)
print fit

Thx Seb!

2011/12/14 Benjamin Root <ben.root@...1304...>:

···

On Wednesday, December 14, 2011, Fabien Lafont <lafont.fabien@...287...> > wrote:

I have a basic problem (I think)

I try to fit some data with this function

http://docs.scipy.org/doc/numpy/reference/generated/numpy.polynomial.Chebyshev.fit.html

But it return an error:

fit = chebyshev.fit(T,R,3)
NameError: name 'chebyshev' is not defined

I don't understand I've imported Numpy and polynomials... An Idea?

import math
from numpy import *
from numpy import polynomial
from pylab import *
from scipy import *
from scipy import optimize
import warnings
warnings.simplefilter('ignore', np.RankWarning)

R = [ 9011.5 , 7822.7 , 6253.9 , 4877.56 , 3892.08 ,
3221.41 , 2647.05,
2260.94 , 1959.72 , 1712.06 , 1522.28 , 1367.87 , 1242.953
, 1185.092,
1104.452 , 1031.862 , 919.8644 , 832.9942 , 767.8944 , 715.1569,
671.6301 , 635.1634 , 604.284 , 577.5536]

T = range(0,len(R))
plot (T,R,".")
show()
fit = chebyshev.fit(T,R,3)
print fit

The function would be in the "polynomial" namespace. So
"polynomial.chebyshev()" would work. To reduce typing, you can import a
module "as" some other name.

from numpy import polynomial as poly

..

fit = poly.chebyshev.fit(T,R,3)

Importing modules is very flexible and I suggest reading up on it.

Ben Root