numpy.polynomial.chebyshev.chebtrim

numpy.polynomial.chebyshev.chebtrim(c, tol=0)

Remove “small” “trailing” coefficients from a polynomial.

“Small” means “small in absolute value” and is controlled by the parameter tol; “trailing” means highest order coefficient(s), e.g., in [0, 1, 1, 0, 0] (which represents 0 + x + x**2 + 0*x**3 + 0*x**4) both the 3-rd and 4-th order coefficients would be “trimmed.”

Parameters:

c : array_like

1-d array of coefficients, ordered from lowest order to highest.

tol : number, optional

Trailing (i.e., highest order) elements with absolute value less than or equal to tol (default value is zero) are removed.

Returns:

trimmed : ndarray

1-d array with trailing zeros removed. If the resulting series would be empty, a series containing a single zero is returned.

Raises:

ValueError

If tol < 0

See also

trimseq

Examples

>>> from numpy import polynomial as P
>>> P.trimcoef((0,0,3,0,5,0,0))
array([ 0.,  0.,  3.,  0.,  5.])
>>> P.trimcoef((0,0,1e-3,0,1e-5,0,0),1e-3) # item == tol is trimmed
array([ 0.])
>>> i = complex(0,1) # works for complex
>>> P.trimcoef((3e-4,1e-3*(1-i),5e-4,2e-5*(1+i)), 1e-3)
array([ 0.0003+0.j   ,  0.0010-0.001j])