scipy.interpolate.PPoly

class scipy.interpolate.PPoly(c, x, extrapolate=None, axis=0)

Piecewise polynomial in terms of coefficients and breakpoints

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

S = sum(c[m, i] * (xp - x[i])**(k-m) for m in range(k+1))

where k is the degree of the polynomial.

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 or ‘periodic’, 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

BPoly

piecewise polynomials in the Bernstein basis

Notes

High-order polynomials in the power basis can be numerically unstable. Precision problems can start to appear for orders larger than 20-30.

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.
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.
solve([y, discontinuity, extrapolate])	Find real solutions of the the equation pp(x) == y.
roots([discontinuity, extrapolate])	Find real roots of the the piecewise polynomial.
extend(c, x[, right])	Add additional breakpoints and coefficients to the polynomial.
from_spline(tck[, extrapolate])	Construct a piecewise polynomial from a spline
from_bernstein_basis(bp[, extrapolate])	Construct a piecewise polynomial in the power basis from a polynomial in Bernstein basis.
construct_fast(c, x[, extrapolate, axis])	Construct the piecewise polynomial without making checks.

scipy.interpolate.CubicSpline.roots scipy.interpolate.PPoly.__call__