function x = unitsig(seq,N,delay)
%  unitsig --> Unit sample, unit step, and unit ramp sequences.
%
%  <Synopsis>
%    x = unitsig(seq,N,delay)
%
%  <Description>
%    Generates an N-vector, which is a unit sample (delta),
%    unit step, or unit ramp sequence, if seq = 'delta',
%    'step', or 'ramp', respectively. The argument, delay,
%    is the number of zero-valued samples in the beginning
%    of the sequences.
%
%  <See Also>
%    sinsig  --> Sum of sinusoidal sequences.
%    rectsig --> Sum of square wave sequences.
%    trisig  --> Sum of sawtooth wave sequences.

%  <Revision>
%    Peter S.K. Hansen, IMM, Technical University of Denmark
%
%    Last revised: February 7, 2000
%-----------------------------------------------------------------------

% Check the required input arguments.
if (nargin < 2)
  error('Not enough input arguments.')
elseif (nargin == 2)
  delay = 0;
end

if (delay >= N)
  error('The delay must be less than the sequence length N.')
end

% Generate the sequence.
if (seq(1)=='d')
  % Delta sequence.
  x = [zeros(delay,1); 1; zeros(N-delay-1,1)];
elseif (seq(1)=='s')
  % Unit step sequence.
  x = [zeros(delay,1); ones(N-delay,1)];
elseif (seq(1)=='r')
  % Unit ramp sequence.
  x = [zeros(delay,1); (0:(N-delay-1))'];
end

%-----------------------------------------------------------------------
% End of function unitsig
%-----------------------------------------------------------------------