Polynomial Interpolation Using Equispaced versus Chebyshev-Lobatto Points

Initializing live version
Download to Desktop

Requires a Wolfram Notebook System

Interact on desktop, mobile and cloud with the free Wolfram Player or other Wolfram Language products.

This Demonstration plots in the interval as well as the function's polynomial interpolation for equally spaced points and for the Chebyshev–Lobatto points.


In the discrete Chebyshev–Gauss–Lobatto case, the interior points are given by . These points are the extremums of the Chebyshev polynomial of the first kind .

You can change the degree of interpolation or the number of interior interpolation points, . As gets larger, the error (computed as the norm of vector with varying from to with a spacing of 0.005), displayed with the red text in the figure, decreases exponentially for the Chebyshev–Lobatto points, while the same computed error increases exponentially in the equispaced case. This behavior is known as the Runge phenomenon.


Contributed by: Housam Binous, Brian G. Higgins, and Ahmed Bellagi (March 2013)
Open content licensed under CC BY-NC-SA




[1] L. N. Trefethen, Spectral Methods in Matlab, Philadelphia: SIAM, 2000.

Feedback (field required)
Email (field required) Name
Occupation Organization
Note: Your message & contact information may be shared with the author of any specific Demonstration for which you give feedback.