function f=partialsum(L,an,bn,t,nmax)
 
  $Id: partialsum.m,v 1.9.1.12 2003-01-04 03:58:58-06 brinkman Exp $
  (c) 2001, Peter Brinkmann (brinkman@math.uiuc.edu)
 
  partialsum: evaluates partial sums of Fourier series.
 
  Usage: f=partialsum(pi,0,[3,2,1],[-1,5,1],linspace(-pi,pi,100),3);
 
  Parameters:
 	L: half period
 	an, bn: column vectors of Fourier coefficients
 	t: row vector of t-values
 	nmax: (optional) maximal summation index
 
  Returns:
 	f: grid of partial sums evaluated at t, i.e.,
 		f(i,:)= (i-1)th partial sum evaluated at t