[SciPy-user] spline interpolation
Robert Kern
robert.kern at gmail.com
Thu Nov 9 16:54:40 CST 2006
Jordan Dawe wrote:
> I've been looking at scipy's interpolation routines and I can't make
> heads or tails of them. I just want to do a spline interp1d like matlab
> does. Is there any way to do this?
I don't know exactly what features you want from Matlab's interp1d, but you
probably want scipy.interpolate.UnivariateSpline.
In [92]: from scipy import interpolate
In [93]: interpolate?
Type: module
Base Class: <type 'module'>
Namespace: Interactive
File:
/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/scipy-0.5.2.dev2310-py2.5-macosx-10.4-i386.egg
/scipy/interpolate/__init__.py
Docstring:
Interpolation Tools
===================
Wrappers around FITPACK functions:
splrep -- find smoothing spline given (x,y) points on curve.
splprep -- find smoothing spline given parametrically defined curve.
splev -- evaluate the spline or its derivatives.
splint -- compute definite integral of a spline.
sproot -- find the roots of a cubic spline.
spalde -- compute all derivatives of a spline at given points.
bisplrep -- find bivariate smoothing spline representation.
bisplev -- evaluate bivariate smoothing spline.
UnivariateSpline -- A more recent, object-oriented wrapper;
finds a (possibly smoothed) interpolating
spline.
InterpolatedUnivariateSpline
LSQUnivariateSpline
BivariateSpline -- A more recent, object-oriented wrapper;
finds a interpolating spline for a
bivariate function.
SmoothBivariateSpline
Interpolation Class
interp1d -- Create a class whose instances can linearly interpolate
to compute unknown values of a univariate function.
interp2d -- Create a class whose instances can interpolate
to compute unknown values of a bivariate function.
In [95]: interpolate.UnivariateSpline?
Type: type
Base Class: <type 'type'>
Namespace: Interactive
File:
/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site-packages/scipy-0.5.2.dev2310-py2.5-macosx-10.4-i386.egg/scipy/interpolate/fitpack2.py
Docstring:
Univariate spline s(x) of degree k on the interval
[xb,xe] calculated from a given set of data points
(x,y).
Can include least-squares fitting.
See also:
splrep, splev, sproot, spint, spalde - an older wrapping of FITPACK
BivariateSpline - a similar class for bivariate spline interpolation
In [99]: from numpy import *
In [100]: x = linspace(0, 2, num=201)
In [101]: x = linspace(0, 2, num=21)
In [102]: y = sin(x*pi)
In [103]: us = interpolate.UnivariateSpline(x, y, s=0.0)
In [104]: x2 = linspace(0, 2, num=201)
In [105]: y2 = us(x2)
--
Robert Kern
"I have come to believe that the whole world is an enigma, a harmless enigma
that is made terrible by our own mad attempt to interpret it as though it had
an underlying truth."
-- Umberto Eco
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