[R] legendre quadrature

[Enrico Schumann]

On Thu, 01 May 2014, pari hesabi <statistics84 at hotmail.com> writes:

> Hello everybody
> I need to approximate the amount of integral by using
>  legendre quadrature. I have written a program which doesn't give me a 
> logical answer; Can anybody help me and send the correct program? For 
> example  the approximated amount of integral of ( x ^2)  on (-1,1) based
>  on legendre quad rule. 
>   

One possibility:

  require("NMOF")
  xw <-xwGauss(10, "legendre")

  fun <- function(x)
      x^2

  sum(fun(xw$nodes) * xw$weights)

>
>
> integrand<-function(x) {x^2}
> rules <- legendre.quadrature.rules( 50 )

  Error: object 'legendre.quadrature.rules' not found

PLEASE "provide commented, minimal, self-contained, reproducible code".

> order.rule <- rules[[50]]
> chebyshev.c.quadrature(integrand, order.rule, lower = -1, upper = 1) 
>
> Thank you
> Diba 		 	   		   		 	   		  

-- 
Enrico Schumann
Lucerne, Switzerland
http://enricoschumann.net