numpy.polyder(p, m=1)
[source]
Return the derivative of the specified order of a polynomial.
Parameters: |
p : poly1d or sequence Polynomial to differentiate. A sequence is interpreted as polynomial coefficients, see m : int, optional Order of differentiation (default: 1) |
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Returns: |
der : poly1d A new polynomial representing the derivative. |
The derivative of the polynomial is:
>>> p = np.poly1d([1,1,1,1]) >>> p2 = np.polyder(p) >>> p2 poly1d([3, 2, 1])
which evaluates to:
>>> p2(2.) 17.0
We can verify this, approximating the derivative with (f(x + h) - f(x))/h
:
>>> (p(2. + 0.001) - p(2.)) / 0.001 17.007000999997857
The fourth-order derivative of a 3rd-order polynomial is zero:
>>> np.polyder(p, 2) poly1d([6, 2]) >>> np.polyder(p, 3) poly1d([6]) >>> np.polyder(p, 4) poly1d([ 0.])
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https://docs.scipy.org/doc/numpy-1.12.0/reference/generated/numpy.polyder.html