papyri
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bundles / scipy latest / scipy / interpolate / _fitpack2 / UnivariateSpline / roots

function

scipy.interpolate._fitpack2:UnivariateSpline.roots

source: /scipy/interpolate/_fitpack2.py :502

Signature

def   roots ( self )

Summary

Return the zeros of the spline.

Notes

Restriction: only cubic splines are supported by FITPACK. For non-cubic splines, use PPoly.root (see below for an example).

Examples

For some data, this method may miss a root. This happens when one of the spline knots (which FITPACK places automatically) happens to coincide with the true root. A workaround is to convert to `PPoly`, which uses a different root-finding algorithm. For example, 
x = [1.96, 1.97, 1.98, 1.99, 2.00, 2.01, 2.02, 2.03, 2.04, 2.05]
y = [-6.365470e-03, -4.790580e-03, -3.204320e-03, -1.607270e-03,
     4.440892e-16,  1.616930e-03,  3.243000e-03,  4.877670e-03,
     6.520430e-03,  8.170770e-03]
from scipy.interpolate import UnivariateSpline
spl = UnivariateSpline(x, y, s=0)
spl.roots()
✓
Converting to a PPoly object does find the roots at `x=2`: 
from scipy.interpolate import splrep, PPoly
tck = splrep(x, y, s=0)
ppoly = PPoly.from_spline(tck)
ppoly.roots(extrapolate=False)
✓

See also

PPoly.roots
sproot

Aliases

  • scipy.interpolate.UnivariateSpline.roots