Differentiate a Chebyshev series.
Returns the series cs differentiated m times. At each iteration the result is multiplied by scl (the scaling factor is for use in a linear change of variable). The argument cs is the sequence of coefficients from lowest order “term” to highest, e.g., [1,2,3] represents the series T_0 + 2*T_1 + 3*T_2.
Parameters : | cs: array_like :
m : int, optional
scl : scalar, optional
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Returns : | der : ndarray
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See also
Notes
In general, the result of differentiating a C-series needs to be “re-projected” onto the C-series basis set. Thus, typically, the result of this function is “un-intuitive,” albeit correct; see Examples section below.
Examples
>>> from numpy.polynomial import chebyshev as C
>>> cs = (1,2,3,4)
>>> C.chebder(cs)
array([ 14., 12., 24.])
>>> C.chebder(cs,3)
array([ 96.])
>>> C.chebder(cs,scl=-1)
array([-14., -12., -24.])
>>> C.chebder(cs,2,-1)
array([ 12., 96.])