Module « numpy.matlib »

Classe « poly1d »

Informations générales

Héritage

builtins.object
    poly1d

Définition

class poly1d(builtins.object):

Description _{[extrait de poly1d.__doc__]}

    A one-dimensional polynomial class.

    .. note::
       This forms part of the old polynomial API. Since version 1.4, the
       new polynomial API defined in `numpy.polynomial` is preferred.
       A summary of the differences can be found in the
       :doc:`transition guide </reference/routines.polynomials>`.

    A convenience class, used to encapsulate "natural" operations on
    polynomials so that said operations may take on their customary
    form in code (see Examples).

    Parameters
    ----------
    c_or_r : array_like
        The polynomial's coefficients, in decreasing powers, or if
        the value of the second parameter is True, the polynomial's
        roots (values where the polynomial evaluates to 0).  For example,
        ``poly1d([1, 2, 3])`` returns an object that represents
        :math:`x^2 + 2x + 3`, whereas ``poly1d([1, 2, 3], True)`` returns
        one that represents :math:`(x-1)(x-2)(x-3) = x^3 - 6x^2 + 11x -6`.
    r : bool, optional
        If True, `c_or_r` specifies the polynomial's roots; the default
        is False.
    variable : str, optional
        Changes the variable used when printing `p` from `x` to `variable`
        (see Examples).

    Examples
    --------
    Construct the polynomial :math:`x^2 + 2x + 3`:

    >>> p = np.poly1d([1, 2, 3])
    >>> print(np.poly1d(p))
       2
    1 x + 2 x + 3

    Evaluate the polynomial at :math:`x = 0.5`:

    >>> p(0.5)
    4.25

    Find the roots:

    >>> p.r
    array([-1.+1.41421356j, -1.-1.41421356j])
    >>> p(p.r)
    array([ -4.44089210e-16+0.j,  -4.44089210e-16+0.j]) # may vary

    These numbers in the previous line represent (0, 0) to machine precision

    Show the coefficients:

    >>> p.c
    array([1, 2, 3])

    Display the order (the leading zero-coefficients are removed):

    >>> p.order
    2

    Show the coefficient of the k-th power in the polynomial
    (which is equivalent to ``p.c[-(i+1)]``):

    >>> p[1]
    2

    Polynomials can be added, subtracted, multiplied, and divided
    (returns quotient and remainder):

    >>> p * p
    poly1d([ 1,  4, 10, 12,  9])

    >>> (p**3 + 4) / p
    (poly1d([ 1.,  4., 10., 12.,  9.]), poly1d([4.]))

    ``asarray(p)`` gives the coefficient array, so polynomials can be
    used in all functions that accept arrays:

    >>> p**2 # square of polynomial
    poly1d([ 1,  4, 10, 12,  9])

    >>> np.square(p) # square of individual coefficients
    array([1, 4, 9])

    The variable used in the string representation of `p` can be modified,
    using the `variable` parameter:

    >>> p = np.poly1d([1,2,3], variable='z')
    >>> print(p)
       2
    1 z + 2 z + 3

    Construct a polynomial from its roots:

    >>> np.poly1d([1, 2], True)
    poly1d([ 1., -3.,  2.])

    This is the same polynomial as obtained by:

    >>> np.poly1d([1, -1]) * np.poly1d([1, -2])
    poly1d([ 1, -3,  2])

    

Constructeur(s)

Signature du constructeur	Description
__init__(self, c_or_r, r=False, variable=None)

Opérateurs hérités de la classe object

__ge__, __gt__, __le__, __lt__

Méthodes héritées de la classe object

__delattr__, __dir__, __format__, __getattribute__, __hash__, __init_subclass__, __reduce__, __reduce_ex__, __setattr__, __sizeof__, __subclasshook__