
Daniel,
 
    That's it!  Thanks.  Your help is very much appreciated.  I'm hoping to nail down the code conversion from MATLAB to R, but it seems to be a bit more difficult that I had anticipated.
 
Craig
 
> From: djnordlund@frontier.com
> To: djnordlund@frontier.com; r-help@r-project.org
> Date: Mon, 11 Oct 2010 16:12:48 -0700
> Subject: Re: [R] MATLAB vrs. R
> 
> I apologize for the noise. I didn't clean up the code enough. See below.
> 
> <<<snip>>>
> > 
> > Craig,
> > 
> > I haven't seen an answer to this yet, so let me jump in. You seem to have
> > some stuff still leftover from MATLAB. Here is some cleaned up code that
> > produces the result you expect. I don't think the value of dx was being
> > correctly computed in your code. I did not change the assignment operator
> > you used (=), but in R the "preferred" operator is "<-" (without the
> > quotes).
> > 
> > myquadrature <- function(f,a,b){
> > npts = length(f)
> > nint = npts-1
> > if(npts <= 1) error('need at least two points to integrate')
> > if(b <= a) error('something wrong with the interval, b should be greater
> > than a') else dx=b/nint
> 
> The 2 'if' statements above should have been
> 
> if(npts <= 1) stop('need at least two points to integrate')
> if(b <= a) stop('something wrong with the interval, b should be greater than a') else dx=b/nint
> 
> > sum(f[-npts]+f[-1])/2*dx
> > }
> > 
> > #Call my quadrature
> > x = seq(0,2000,10)
> > h = 10*(cos(((2*pi)/2000)*(x-mean(x)))+1)
> > u = (cos(((2*pi)/2000)*(x-mean(x)))+1)
> > a = x[1]
> > b = x[length(x)]
> > plot(x,-h)
> > a = x[1];
> > b = x[length(x)]
> > 
> > #call your quadrature function. Hint, the answer should be 30000.
> > f = u*h
> > result = myquadrature(f,a,b)
> > result
> > 
> > Hope this is helpful,
> > 
> > Dan
> > 
> Daniel Nordlund
> Bothell, WA USA
> 
> 
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