On Tue, Jul 3, 2012 at 10:50 AM, Carnë Draug <carandraug+...@gmail.com> wrote: > Hi > > I was looking at the built-in forums of sourceforge and found the > following reported 2 years ago (these forums have since been hidden > and blocked to prevent posting). Could someone please review the > following?
Hey Carnë, I've taken a look at this function and run some test cases against it, I do not think there is a (serious) bug here, see below. > Reported by jmiles1: possible typo in main/signal/inst/fir2.m: > > ## make sure grid is big enough for the window > if 2*grid_n < n+1, grid_n = 2^nextpow2(n+1); endif > > should probably be > > ## make sure grid is big enough for the window > if grid_n < n+1, grid_n = 2^nextpow2(n+1); endif > > Otherwise it looks like there's a range of grid sizes between n/2 and > n that will be smaller than n, and generate an overlapped impulse > response in line 122. Apologies in advance if this was the intent, but > it definitely doesn't jibe with the comment in line 29. The comment is surely not clear about what "big enough" means, but the test for 2*grid_n < n+1 is correct when compared with the rest of the function as well as comparing the ML fir2 help text [1]: "npt must be greater than 1/2 the filter order (npt>n/2)". [1] http://www.mathworks.com/help/toolbox/signal/ref/fir2.html Line 105 interpolates the input to a length (grid_n+1) vector, and lines 111 and 116 replicate this for even spectral symmetry (2*grid_n), and this is the length that must be >= n+1. The only thing that is not clear to me is whether this matches ML behavior, and whether we care, e.g. if the caller passes in a 4th arg too small, does ML generate an error or silently make it larger like this line 29 does? -- mike ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Octave-dev mailing list Octave-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/octave-dev
