function z=ptime(pmatrix,pos)

% This function computes the time domain representation of a periodic waveform
% from its spectral components at a given position.  The output is a vector
% which contains the amplitude of waveform as a function of a scaled time
% (omega*tau) which runs from -pi to pi.
%
% by Ronald Kumon, 2 Dec 1995

% Declare global variables
global a n nhar

% Form waveform
Nsteps=50;
step=2*pi/Nsteps;
%z=zeros(1,Nsteps+1);
index = 1;
pvec    =pmatrix(pos,:);
Avec    =real(pvec);
Bvec    =-imag(pvec);
for y=-pi:step:pi
  compvec =Avec.*cos(n*y)+Bvec.*sin(n*y);
  z(index)=sum(compvec);
  index=index+1;
end
