Questions tagged [spline]
A smooth piecewise-defined curve formed by joining segments together, end-to-end. The segments are usually described by polynomial or rational functions. Splines are typically used for approximation or data fitting.
646 questions
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Is it possible to improve on the trapezoidal rule if we have derivative data available?
If we know the value of a function $f$ at a set of points (usually regularly spaced, but that is not necessary) $x_1, x_2, \dots, x_k$, we can approximate the integral $\int_{x_1}^{x_k} f(x) dx$ via ...
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Boundary values for b splines under clamped knots
I am trying to proof this by induction Proposition (Boundary values under clamped knots): Let $\{t_i\}_{i=1}^{m=n+k}$ be a clamped knot sequence of order $k$ on the interval $[a,b]$, that is, $$ t_1 = ...
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Penalized spline on the circle
I am inquiring about a particular result shown in section 2.1 of Grace Wahba's book (pages 23-24), Spline models for observational data. The setup is as follows. We consider the data model $$y_i = f\...
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Faster approximation for piecewise linear functions in $L^2(\rho)$
Let $I=[0,1]$ be the unit interval, and $f:I\to\mathbb R$ be a $C^2$ function. For $n\ge1$, denote by $PL(n)$ the set of continuous, piecewise linear functions with $n$ pieces defined on $I$. It is a ...
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Dimension of polynomial spline space
Let be $[a,b]$ an interval and $\Delta$ a partition of $[a,b]$ where $a=\xi_0<\xi_1<\dotsc<\xi_n=b$ and $I_j:=(\xi_{j-1},\xi_j)$. Further, let be $l,m\in\mathbb{N}$. We define the space of ...
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How to derive analytic formula or efficient computational scheme for function underlying pseudoinverse to linear interpolation matrix?
Background: I am resizing image dimensions to powers of two for practical purposes in an image compression scheme. Then I need to switch back to the previous size. For example an image of dimensions ...
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Fit nonlinear, increasing and concave function
I have a set of data consisting of water levels [$m$] and volumes [$m^3$] that I want to fit a function to while fulfilling some constraints over the defined region of volumes. An example of a dataset ...
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Carl de Boor's "A Practical Guide to Splines" (2001), page 89, BBform definition
Book on archive.org: https://archive.org/details/practicalguideto0000debo In Carl de Boor's A Practical Guide to Splines (2001/revised edition), page 89, definition of the BBform, corresponding to B-...
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Carl de Boor's "A Practical Guide to Splines" (2001), page 90, particular product
In Carl de Boor's A Practical Guide to Splines (2001), page 90, proof for the B-spline property (i): (archive.org: https://archive.org/details/practicalguideto0000debo) Apply Leibniz' formula I(iv) ...
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Maximum curvature of a Quintic Bezier curve
I am interested in solving the following problem. Let's say we have a quintic bezier curve p(t) = {p0, p1, p2, p3, p4, p5}. I also have some curvature bound Kc. How can I find that the maximum ...
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Finding an optimal interpolation subject to some boundary constraints
Let $s\in \left(0, 1\right)$, and consider the task of finding the 'nicest-possible' function $f$ such that $f(0) = 0, f^\prime (0) = s$, and $f(1) = 1, f^\prime (1) = 0$, where 'niceness' is framed ...
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Is a parametric polynomial curve always a Bézier curve?
I'm a newer to NURBS curves and surfaces stuff. Here is my (naive) question regarding related definitions, and I just want to check my understandings: Is a parametric curve $\gamma(t)=(x(t),y(t),z(t))...
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What formula could mimic loosened thread
I am looking for a formula to make a curve that could mimic loosened thread (from P to Q in the above figure) in 2D. The thread need not be slanted. Wrt x axis I can plot the loosened thread. Which ...
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Draw line along parametric circle intersecting points in order
I have an equation that converts three points $p_0,p_1,p_2$ into a parametric circle where $o$ is the center of the circle and $R$ is the radius. $$ f(t)=(o_x+Rcos(t),o_y+Rsin(t)) $$ this part works ...
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Orders and Degrees - Piecewise Polynomial functions
I was reading through a section in the textbook ESL2 Sec.5.2 (P.144) under Basis Expansions and Regularization when I came across this line: "More generally, an order-$M$ spline with knots $\xi_j$...