--- a/doc/interpreter/contributors.in	Thu Aug 07 11:46:12 2014 -0400
+++ b/doc/interpreter/contributors.in	Thu Aug 07 10:13:30 2014 -0700
@@ -1,4 +1,5 @@
 Ben Abbott
+Drew Abbot
 Andy Adler
 Adam H. Aitkenhead
 Giles Anderson

--- a/scripts/signal/periodogram.m	Thu Aug 07 11:46:12 2014 -0400
+++ b/scripts/signal/periodogram.m	Thu Aug 07 10:13:30 2014 -0700
@@ -1,5 +1,6 @@
 ## Copyright (C) 1995-2013 Friedrich Leisch
 ## Copyright (C) 2010 Alois Schloegl
+## Copyright (C) 2014 Drew Abbot
 ##
 ## This file is part of Octave.
 ##
@@ -18,43 +19,60 @@
 ## <http://www.gnu.org/licenses/>.
 
 ## -*- texinfo -*-
-## @deftypefn {Function File} {[Pxx, @var{w}] =} periodogram (@var{x})
-## For a data matrix @var{x} from a sample of size @var{n}, return the
-## periodogram.  The angular frequency is returned in @var{w}.
+## @deftypefn  {Function File} {[@var{Pxx}, @var{w}] =} periodogram (@var{x})
+## @deftypefnx {Function File} {[@var{Pxx}, @var{w}] =} periodogram (@var{x}, @var{win})
+## @deftypefnx {Function File} {[@var{Pxx}, @var{w}] =} periodogram (@var{x}, @var{win}, @var{nfft})
+## @deftypefnx {Function File} {[@var{Pxx}, @var{f}] =} periodogram (@var{x}, @var{win}, @var{nfft}, @var{Fs})
+## @deftypefnx {Function File} {[@var{Pxx}, @var{f}] =} periodogram (@dots{}, "@var{range}")
+## @deftypefnx {Function File} {} periodogram (@dots{})
 ##
-## [Pxx,w] = periodogram (@var{x}).
+## Return the periodogram (Power Spectral Density) of @var{x}.
 ##
-## [Pxx,w] = periodogram (@var{x},win).
+## The possible inputs are:
 ##
-## [Pxx,w] = periodogram (@var{x},win,nfft).
-##
-## [Pxx,f] = periodogram (@var{x},win,nfft,Fs).
+## @table @var
+## @item x
 ##
-## [Pxx,f] = periodogram (@var{x},win,nfft,Fs,"range").
+## data vector.  If @var{x} is real-valued a one-sided spectrum is estimated.
+## If @var{x} is complex-valued, or @qcode{"@var{range}"} specifies
+## @qcode{"@nospell{twosided}"}, the full spectrum is estimated.
 ##
-## @itemize
-## @item x: data; if real-valued a one-sided spectrum is estimated,
-## if complex-valued or range indicates @qcode{"@nospell{twosided}"}, the full
-## spectrum is estimated.
+## @item win
+## window weight data.  If window is empty or unspecified a default rectangular
+## window is used.  Otherwise, the window is applied to the signal
+## (@code{@var{x} .* @var{win}}) before computing the periodogram.  The window
+## data must be a vector of the same length as @var{x}.
 ##
-## @item win: weight data with window, x.*win is used for further computation,
-## if window is empty, a rectangular window is used.
+## @item nfft
+## number of frequency bins.  The default is 256 or the next higher power of 
+## 2 greater than the length of @var{x}
+## (@code{max (256, 2.^nextpow2 (length (x)))}).  If @var{nfft} is greater
+## than the length of the input then @var{x} will be zero-padded to the length
+## of @var{nfft}.
 ##
-## @item nfft: number of frequency bins, default max (256, 2.^ceil (log2 (length (x)))).
-##
-## @item Fs: sampling rate, default 1.
+## @item Fs
+## sampling rate.  The default is 1.
 ##
-## @item range: @qcode{"@nospell{onesided}"} computes spectrum from [0..nfft/2+1].
-## @qcode{"@nospell{twosided}"} computes spectrum from [0..nfft-1].  These
-## strings can appear at any position in the list input arguments after
-## window.
+## @item range
+## range of spectrum.  @qcode{"@nospell{onesided}"} computes spectrum from
+## [0..nfft/2+1]. @qcode{"@nospell{twosided}"} computes spectrum from
+## [0..nfft-1].
+## @end table
 ##
-## @item @nospell{Pxx}: one-, or two-sided power spectrum.
+## The optional second output @var{w} are the normalized angular frequencies.
+## For a onesided calculation @var{w} is in the range [0, pi] if @var{nfft}
+## is even and [0, pi) if @var{nfft} is odd.  Similarly, for a twosided
+## calculation @var{w} is in the range [0, 2*pi] or [0, 2*pi) depending on
+## @var{nfft}.
 ##
-## @item w: angular frequency [0..2*pi) (two-sided) or [0..pi] one-sided.
-##
-## @item f: frequency [0..Fs) (two-sided) or [0..Fs/2] one-sided.
-## @end itemize
+## If a sampling frequency is specified, @var{Fs}, then the output frequencies
+## @var{f} will be in the range [0, @var{Fs}/2] or [0, @var{Fs}/2) for
+## onesided calculations.  For twosided calculations the range will be
+## [0, @var{Fs}).
+## 
+## When called with no outputs the periodogram is immediately plotted in the
+## current figure window.
+## @seealso{fft}
 ## @end deftypefn
 
 ## Author: FL <Friedrich.Leisch@ci.tuwien.ac.at>
@@ -63,12 +81,11 @@
 function [pxx, f] = periodogram (x, varargin)
 
   ## check input arguments
-
   if (nargin < 1 || nargin > 5)
     print_usage ();
   endif
 
-  nfft = []; fs = []; range = []; window = [];
+  nfft = fs = range = window = [];
   j = 1;
   for k = 1:length (varargin)
     if (ischar (varargin{k}))
@@ -88,66 +105,54 @@
     endif
   endfor
 
-  [r, c] = size (x);
-  if (r == 1)
-    r = c;
+  if (! isvector (x))
+    error ("periodogram: X must be a real or complex vector");
+  endif
+  x = x(:);  # Use column vectors from now on
+  
+  n = rows (x);
+
+  if (! isempty (window))
+    if (! isvector (window) || length (window) != n)
+      error ("periodogram: WIN must be a vector of the same length as X");
+    endif
+    window = window(:);
+    x .*= window;
   endif
 
-  if (ischar (window))
-    range = window;
-    window = [];
-  endif;
-  if (ischar (nfft))
-    range = nfft;
-    nfft = [];
-  endif;
-  if (ischar (fs))
-    range = fs;
-    fs = [];
-  endif;
-
-  if (!  isempty (window))
-    if (all (size (x) == size (window)))
-      x .*= window;
-    elseif (rows (x) == rows (window) && columns (window) == 1)
-      x .*= window (:,ones (1,c));
-    endif;
+  if (isempty (nfft))
+    nfft = max (256, 2.^nextpow2 (n));
+  elseif (! isscalar (nfft))
+    error ("periodogram: NFFT must be a scalar");
   endif
 
-  if (numel (nfft)>1)
-    error ("nfft must be scalar");
-  endif
-  if (isempty (nfft))
-    nfft = max (256, 2.^ceil (log2 (r)));
-  endif
-
-  if (strcmp (range, "onesided"))
+  if (strcmpi (range, "onesided"))
     range = 1;
-  elseif (strcmp (range, "twosided"))
+  elseif (strcmpi (range, "twosided"))
     range = 2;
+  elseif (strcmpi (range, "centered"))
+    error ('periodogram: "centered" range type is not implemented');
   else
     range = 2-isreal (x);
   endif
 
   ## compute periodogram
 
-  if (r>nfft)
+  if (n > nfft)
     Pxx = 0;
     rr = rem (length (x), nfft);
     if (rr)
-      x = [x(:); (zeros (nfft-rr, 1))];
+      x = [x(:); zeros(nfft-rr, 1)];
     endif
     x = sum (reshape (x, nfft, []), 2);
   endif
 
-  if (isempty (window))
-    n = r;
-  else
+  if (! isempty (window))
     n = sumsq (window);
-  end;
-  Pxx = (abs (fft (x, nfft))) .^ 2 / n ;
+  endif;
+  Pxx = (abs (fft (x, nfft))) .^ 2 / n;
 
-  if (nargin<4)
+  if (nargin < 4)
     Pxx /= 2*pi;
   elseif (! isempty (fs))
     Pxx /= fs;
@@ -156,24 +161,30 @@
   ## generate output arguments
 
   if (range == 1)  # onesided
-    Pxx = Pxx(1:nfft/2+1) + [0; Pxx(end:-1:(nfft/2+2)); 0];
+    if (! rem (nfft,2))  # nfft is even
+      psd_len = nfft/2+1;
+      Pxx = Pxx(1:psd_len) + [0; Pxx(nfft:-1:psd_len+1); 0];
+    else                 # nfft is odd
+      psd_len = (nfft+1)/2;
+      Pxx = Pxx(1:psd_len) + [0; Pxx(nfft:-1:psd_len+1)];
+    endif
   endif
 
   if (nargout != 1)
     if (range == 1)
-      f = (0:nfft/2)'/nfft;
+      f = (0:nfft/2)' / nfft;
     elseif (range == 2)
-      f = (0:nfft-1)'/nfft;
+      f = (0:nfft-1)' / nfft;
     endif
-    if (nargin<4)
-      f *= 2*pi; # generate w=2*pi*f
+    if (nargin < 4)
+      f *= 2*pi;  # generate w=2*pi*f
     elseif (! isempty (fs))
       f *= fs;
     endif
   endif
 
   if (nargout == 0)
-    if (nargin<4)
+    if (nargin < 4)
       plot (f/(2*pi), 10*log10 (Pxx));
       xlabel ("normalized frequency [x pi rad]");
       ylabel ("Power density [dB/rad/sample]");
@@ -190,3 +201,16 @@
 
 endfunction
 
+
+## FIXME: Need some functional tests
+
+
+%% Test input validation
+%!error periodogram ()
+%!error periodogram (1,2,3,4,5,6)
+%!error <X must be a real or complex vector> periodogram (ones (2,2))
+%!error <WIN must be a vector.*same length> periodogram (1:5, ones (2,2))
+%!error <WIN must be a vector.*same length> periodogram (1:5, 1:6)
+%!error <NFFT must be a scalar> periodogram (1:5, 1:5, 1:5)
+%!error <"centered" range type is not implemented> periodogram (1:5, "centered")
+