On 7 November 2011 22:42, Jeffrey Cunningham <jeff...@jkcunningham.com> wrote: > On Mon, 07 Nov 2011 10:16:39 -0800, Carnė Draug <carandraug+...@gmail.com> > wrote: > >> On 7 November 2011 16:43, Alberto Cuadrado <a.cuadr...@gmail.com> wrote: >>> >>> Hello, >>> >>> I think there is a bug in the fir1 function in signal-1.0.11 (and >>> probably >>> also in 1.1.1 because I don't see significant changes in the code). The >>> problem is that single-band lowpass filters returned by fir1 don't have a >>> DC >>> gain of 1. For example: >>> >>> octave-3.2.4:1> sum(fir1(240,0.01)) >>> ans = 1.1822 >>> >>> That should return 1 (with low-order filters the problem is not so >>> obvious). >>> >>> Regards >>> >>> Alberto Cuadrado >> >> I can confirm that this still occurs in octave 3.4.3 with signal 1.1. >> Do you think you can contribute a patch to fix this? >> > > > Are you sure it is a bug? I am assuming that you want the filter to be > normalized the same way as Matlab's fir1 function, and they say: > > "By default, the filter is scaled so that the center of the first passband > has a magnitude of exactly 1 after windowing." > > In other words, they are normalizing so the *frequency domain* passband > comes out to 1. The d.c. output level divided by the bandwidth will be > (roughly) 1.
I asked in ##matlab and it seems it returns exactly 1 there. Carnė ------------------------------------------------------------------------------ RSA(R) Conference 2012 Save $700 by Nov 18 Register now http://p.sf.net/sfu/rsa-sfdev2dev1 _______________________________________________ Octave-dev mailing list Octave-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/octave-dev
