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A mathematical expression w/ >1 term containing the same variable (eg, x & x^2). Polynomials are commonly used to model curvilinear relationships.

2 votes
1 answer
847 views

How to algorithmically determine the best order of fit?

I am doing a least squares polynomial interpolation for 10,000 data sets that look mostly like one period of a sine curve, but whose values are not evenly spaced in the time domain, and can sometimes be …
rhombidodecahedron's user avatar
4 votes
1 answer
1k views

What is the second derivative of a B-spline?

A B-spline of degree $j$ is defined at knots $\vec k$ by the Cox-de Boor recursion formula \begin{align} B_{i,1}(x) &= \left\{ \begin{matrix} 1 & \mathrm{if} \quad k_i \leq x …
rhombidodecahedron's user avatar
6 votes
Accepted

What is the second derivative of a B-spline?

This document gives (with a corrected typo) \begin{equation} \frac{\text{d}^{(n)}B_{i,j}(x)}{\text{d}x^{(n)}} = (j-1) \left( \frac{- \text{d}^{(n-1)} B_{i+1,j-1}(x) / \text{d} …
rhombidodecahedron's user avatar