Classe « BSpline »

Méthode scipy.interpolate.BSpline.basis_element

Signature de la méthode basis_element

def basis_element(t, extrapolate=True) 

Description

basis_element.__doc__

Return a B-spline basis element ``B(x | t[0], ..., t[k+1])``.

        Parameters
        ----------
        t : ndarray, shape (k+1,)
            internal knots
        extrapolate : bool or 'periodic', optional
            whether to extrapolate beyond the base interval, ``t[0] .. t[k+1]``,
            or to return nans.
            If 'periodic', periodic extrapolation is used.
            Default is True.

        Returns
        -------
        basis_element : callable
            A callable representing a B-spline basis element for the knot
            vector `t`.

        Notes
        -----
        The degree of the B-spline, `k`, is inferred from the length of `t` as
        ``len(t)-2``. The knot vector is constructed by appending and prepending
        ``k+1`` elements to internal knots `t`.

        Examples
        --------

        Construct a cubic B-spline:

        >>> from scipy.interpolate import BSpline
        >>> b = BSpline.basis_element([0, 1, 2, 3, 4])
        >>> k = b.k
        >>> b.t[k:-k]
        array([ 0.,  1.,  2.,  3.,  4.])
        >>> k
        3

        Construct a quadratic B-spline on ``[0, 1, 1, 2]``, and compare
        to its explicit form:

        >>> t = [-1, 0, 1, 1, 2]
        >>> b = BSpline.basis_element(t[1:])
        >>> def f(x):
        ...     return np.where(x < 1, x*x, (2. - x)**2)

        >>> import matplotlib.pyplot as plt
        >>> fig, ax = plt.subplots()
        >>> x = np.linspace(0, 2, 51)
        >>> ax.plot(x, b(x), 'g', lw=3)
        >>> ax.plot(x, f(x), 'r', lw=8, alpha=0.4)
        >>> ax.grid(True)
        >>> plt.show()