[Octave-bug-tracker] [bug #42859] bugs in periodogram.m

[Drew Abbot]

Follow-up Comment #3, bug #42859 (project octave):

As far as I can tell, as of MATLAB 2013a:


 pxx = periodogram (1:8, [], 4)


yields [ 25.7831 ; 1.2732 ; 0.3183 ], and Octave yields the same result.

However, in MATLAB, the following also yields that same result (as it should)


 pxx = periodogram (1:8, [], 4, 'onesided')


but in Octave, the result is [ 162 ; 8 ; 2 ], which is the same result as
before but scaled by (2*pi).  This is related to both the code


 if (nargin<4)
   Pxx /= 2*pi;
 elseif (! isempty (fs))
   Pxx /= fs;
 endif


and the fact that fs is initialized to [].  To get around this, fs could be
initialized to 2*pi, or to be even more complete, multiple MATLAB
compatibility modes could be supported (as is done in the Octave signal
package's pwelch() method), with default fs values of 1.0 or 2*pi accordingly.




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