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Splines and their properties and applications. A spline is a function defined piecewise by polynomials, and is typically used in interpolating problems.

1 vote
Accepted

Spline Interpolation error of higher degree

The following paper by de Boor suggests that this is the case, although he develops the proof only up to degree 6 splines. de Boor, C., On the convergence of odd-degree spline interpolation, J. …
Iddo Hanniel's user avatar
2 votes

Relation between Cox-deBoor recursion and Convolution (b-spline basis)

The B-Spline basis functions as defined by the Cox-DeBoor formula cannot, in general, be constructed with convolution. The convolution construction, as I'll explain below, only works for the special c …
gmvh's user avatar
  • 3,065
1 vote
Accepted

General reparameterization of a B-spline

B-splines are a basis-function representation for piecwise polynomial functions. …
Iddo Hanniel's user avatar
1 vote

Bounds on the second derivative of a natural cubic spline in terms of the data

However, I believe the most straightforward way to attain them in our context is in constructions of cubic splines that begin by integrating the second derivative constraints. …
Iddo Hanniel's user avatar
0 votes
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Rule to determine rotationally invariant orders of the points of arbitrary 2d splines

First, if there is a rotational symmetry in the curve, for example a line segment or an S-shape, then you cannot achieve your goal since the 180-degree rotated curve is exactly identical to the origin …
Iddo Hanniel's user avatar
3 votes
Accepted

Interpolation nodes for linear spline (piecewise-linear) interpolation of $x \ln x$

There is an analytical solution to the problem in the following sense: Given a number $N$, the optimal interpolation points $x_0=0, x_1, ..., x_{N-1}=1$ are the roots of an $(N-2) \times (N-2)$ syste …
Iddo Hanniel's user avatar
1 vote

Polynomial-preserving boundary conditions for spline interpolation

There are no generic boundary conditions that guarantee that the interpolating spline reproduces a sampled polynomial. On the other hand, any $p-1$ conditions (where $p$ is the spline polynomial degre …
Iddo Hanniel's user avatar
3 votes

Do splines preserve monotonicity?

Not only is the answer "no", but for any number $N$ you can construct a monotone function and sample it such that the natural spline approximation will have $N$ extremum points. See the figure (and i …
Iddo Hanniel's user avatar
3 votes
Accepted

Optimal $L^2$ bounds of cubic spline interpolation

These polynomials are what the inner splines in the example converge to. The last thing that is left to do is to show that we can build a similar construction with a $C^4$ function. …
Iddo Hanniel's user avatar
3 votes

Integrating B-Spline composed with log

The $\int_a^b f(\log x) dx$ expression actually has a nice analytical form, which enables to evaluate it in an elegant manner. First, we perform a change of variables $y=\log x$, $dx = x dy = e^y dy$ …
Iddo Hanniel's user avatar
2 votes

Splines with bounded first derivative?

This is an interesting question and as @user100927 has correctly commented, a necessary condition for this to be possible is: $$\int_{x_i}^{x_{i+1}}f(x)dx ≤ y_{i+1}−y_i$$ for all $i$. To prove this c …
Iddo Hanniel's user avatar
4 votes

Maximum of a B-spline

Using the recursive derivative formula (see for example here): $$N'_{i,p}(t) = \frac{p}{t_{i+p}-t_i} N_{i,p-1}(t) - \frac{p}{t_{i+p+1}-t_{i+1}} N_{i+1,p-1}(t)$$ We get that the maximum is achieved whe …
Iddo Hanniel's user avatar
1 vote

Cubic interpolating spline – number of extremum points

The final bound, which I will develop using B-Splines, is $n-1$. I'll also show that his bound is tight. … However, as I said above, we can do better using the theory of B-Splines. …
Iddo Hanniel's user avatar