scipy.interpolate.BPoly#

class scipy.interpolate.BPoly(c, x, extrapolate=None, axis=0)[source]#

Piecewise polynomial in terms of coefficients and breakpoints.

The polynomial between x[i] and x[i + 1] is written in the Bernstein polynomial basis:

S = sum(c[a, i] * b(a, k; x) for a in range(k+1)),

where k is the degree of the polynomial, and:

b(a, k; x) = binom(k, a) * t**a * (1 - t)**(k - a),

with t = (x - x[i]) / (x[i+1] - x[i]) and binom is the binomial coefficient.

Parameters

cndarray, shape (k, m, …): Polynomial coefficients, order k and m intervals
xndarray, shape (m+1,): Polynomial breakpoints. Must be sorted in either increasing or decreasing order.
extrapolatebool, optional: If bool, determines whether to extrapolate to out-of-bounds points based on first and last intervals, or to return NaNs. If ‘periodic’, periodic extrapolation is used. Default is True.
axisint, optional: Interpolation axis. Default is zero.

See also

PPoly: piecewise polynomials in the power basis

Notes

Properties of Bernstein polynomials are well documented in the literature, see for example [1] [2] [3].

References

1: https://en.wikipedia.org/wiki/Bernstein_polynomial
2: Kenneth I. Joy, Bernstein polynomials, http://www.idav.ucdavis.edu/education/CAGDNotes/Bernstein-Polynomials.pdf
3: E. H. Doha, A. H. Bhrawy, and M. A. Saker, Boundary Value Problems, vol 2011, article ID 829546, DOI:10.1155/2011/829543.

Examples

>>> from scipy.interpolate import BPoly
>>> x = [0, 1]
>>> c = [[1], [2], [3]]
>>> bp = BPoly(c, x)

This creates a 2nd order polynomial

\[\begin{split}B(x) = 1 \times b_{0, 2}(x) + 2 \times b_{1, 2}(x) + 3 \times b_{2, 2}(x) \\ = 1 \times (1-x)^2 + 2 \times 2 x (1 - x) + 3 \times x^2\end{split}\]

Attributes

xndarray: Breakpoints.
cndarray: Coefficients of the polynomials. They are reshaped to a 3-D array with the last dimension representing the trailing dimensions of the original coefficient array.
axisint: Interpolation axis.

Methods

`__call__`(x[, nu, extrapolate])	Evaluate the piecewise polynomial or its derivative.
`extend`(c, x[, right])	Add additional breakpoints and coefficients to the polynomial.
`derivative`([nu])	Construct a new piecewise polynomial representing the derivative.
`antiderivative`([nu])	Construct a new piecewise polynomial representing the antiderivative.
`integrate`(a, b[, extrapolate])	Compute a definite integral over a piecewise polynomial.
`construct_fast`(c, x[, extrapolate, axis])	Construct the piecewise polynomial without making checks.
`from_power_basis`(pp[, extrapolate])	Construct a piecewise polynomial in Bernstein basis from a power basis polynomial.
`from_derivatives`(xi, yi[, orders, extrapolate])	Construct a piecewise polynomial in the Bernstein basis, compatible with the specified values and derivatives at breakpoints.

scipy.interpolate.PPoly.construct_fast

scipy.interpolate.BPoly.__call__