scipy.interpolate.CubicSpline.solve#

CubicSpline.solve(y=0.0, discontinuity=True, extrapolate=None)[source]#

Find real solutions of the equation pp(x) == y.

Parameters:

yfloat, optional: Right-hand side. Default is zero.
discontinuitybool, optional: Whether to report sign changes across discontinuities at breakpoints as roots.
extrapolate{bool, ‘periodic’, None}, optional: If bool, determines whether to return roots from the polynomial extrapolated based on first and last intervals, ‘periodic’ works the same as False. If None (default), use self.extrapolate.

Returns:

rootsndarray

Roots of the polynomial(s).

If the PPoly object describes multiple polynomials, the return value is an object array whose each element is an ndarray containing the roots.

Notes

This routine works only on real-valued polynomials.

If the piecewise polynomial contains sections that are identically zero, the root list will contain the start point of the corresponding interval, followed by a nan value.

If the polynomial is discontinuous across a breakpoint, and there is a sign change across the breakpoint, this is reported if the discont parameter is True.

Examples

Finding roots of [x**2 - 1, (x - 1)**2] defined on intervals [-2, 1], [1, 2]:

>>> import numpy as np
>>> from scipy.interpolate import PPoly
>>> pp = PPoly(np.array([[1, -4, 3], [1, 0, 0]]).T, [-2, 1, 2])
>>> pp.solve()
array([-1.,  1.])