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Difference between revisions of "Lobatto quadrature formula"

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A quadrature formula of highest algebraic degree of accuracy for the interval <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l0600601.png" /> and weight <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l0600602.png" /> with two fixed nodes: the end-points of <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l0600603.png" />. The Lobatto quadrature formula has the form
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A quadrature formula of highest algebraic degree of accuracy for the interval $[a,b]=[-1,1]$ and weight $p(x)=1$ with two fixed nodes: the end-points of $[-1,1]$. The Lobatto quadrature formula has the form
  
<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l0600604.png" /></td> </tr></table>
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$$\int\limits_{-1}^1f(x)dx\cong A[f(-1)+f(1)]+\sum_{j=1}^nC_jf(x_j).$$
  
The points <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l0600605.png" /> are the roots of the polynomial <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l0600606.png" /> (a Jacobi polynomial), orthogonal on <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l0600607.png" /> with respect to the weight <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l0600608.png" />, <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l0600609.png" /> and <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l06006010.png" />. The algebraic degree of accuracy is <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l06006011.png" />. A table of nodes and coefficients of the Lobatto quadrature formula for <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l06006012.png" /> (<img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/l/l060/l060060/l06006013.png" /> varies from 1 to 15 with step 1) was given in [[#References|[2]]] (see also [[#References|[3]]]).
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The points $x_j$ are the roots of the polynomial $P_n^{(1,1)}(x)$ (a Jacobi polynomial), orthogonal on $[-1,1]$ with respect to the weight $1-x^2$, $A=2/(n+1)(n+2)$ and $C_j>0$. The algebraic degree of accuracy is $2n+1$. A table of nodes and coefficients of the Lobatto quadrature formula for $n=1(1)15$ ($n$ varies from 1 to 15 with step 1) was given in [[#References|[2]]] (see also [[#References|[3]]]).
  
 
The formula was established by R. Lobatto (see [[#References|[1]]]).
 
The formula was established by R. Lobatto (see [[#References|[1]]]).

Revision as of 15:30, 13 October 2014

A quadrature formula of highest algebraic degree of accuracy for the interval $[a,b]=[-1,1]$ and weight $p(x)=1$ with two fixed nodes: the end-points of $[-1,1]$. The Lobatto quadrature formula has the form

$$\int\limits_{-1}^1f(x)dx\cong A[f(-1)+f(1)]+\sum_{j=1}^nC_jf(x_j).$$

The points $x_j$ are the roots of the polynomial $P_n^{(1,1)}(x)$ (a Jacobi polynomial), orthogonal on $[-1,1]$ with respect to the weight $1-x^2$, $A=2/(n+1)(n+2)$ and $C_j>0$. The algebraic degree of accuracy is $2n+1$. A table of nodes and coefficients of the Lobatto quadrature formula for $n=1(1)15$ ($n$ varies from 1 to 15 with step 1) was given in [2] (see also [3]).

The formula was established by R. Lobatto (see [1]).

References

[1] R. Lobatto, "Lessen over de differentiaal- en integraalrekening" , 1–2 , 's Gravenhage (1851–1852)
[2] V.I. Krylov, "Approximate calculation of integrals" , Macmillan (1962) (Translated from Russian)
[3] H.H. Michels, "Abscissas and weight coefficients for Lobatto quadrature" Math. Comp. , 17 (1963) pp. 237–244


Comments

For the notion of algebraic degree of accuracy of a quadrature formula see Quadrature formula.

References

[a1] A.H. Stroud, "Gaussian quadrature formulas" , Prentice-Hall (1966)
How to Cite This Entry:
Lobatto quadrature formula. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Lobatto_quadrature_formula&oldid=11333
This article was adapted from an original article by I.P. Mysovskikh (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article