Revision: 10874
http://octave.svn.sourceforge.net/octave/?rev=10874&view=rev
Author: mtmiller
Date: 2012-08-15 06:33:49 +0000 (Wed, 15 Aug 2012)
Log Message:
-----------
fir2: fix default frequency response interpolation parameters
* Increase default interpolation size for larger filter length.
* Default transition width is 1/25 of interpolation size.
Modified Paths:
--------------
trunk/octave-forge/main/signal/inst/fir2.m
Modified: trunk/octave-forge/main/signal/inst/fir2.m
===================================================================
--- trunk/octave-forge/main/signal/inst/fir2.m 2012-08-14 20:50:42 UTC (rev 10873)
+++ trunk/octave-forge/main/signal/inst/fir2.m 2012-08-15 06:33:49 UTC (rev 10874)
@@ -28,7 +28,7 @@
## grid_n: length of ideal frequency response function
## defaults to 512, should be a power of 2 bigger than n/2
## ramp_n: transition width for jumps in filter response
-## defaults to grid_n/20; a wider ramp gives wider transitions
+## defaults to grid_n/25; a wider ramp gives wider transitions
## but has better stopband characteristics.
## window: smoothing window
## defaults to hamming(n+1) row vector
@@ -75,7 +75,14 @@
if !isreal(window) || ischar(window), window=feval(window, n+1); endif
if length(window) != n+1, usage("window must be of length n+1"); endif
- if isempty (grid_n), grid_n = 512; endif
+ ## Default grid size is 512... unless n+1 >= 1024
+ if isempty (grid_n)
+ if n+1 < 1024
+ grid_n = 512;
+ else
+ grid_n = n+1;
+ endif
+ endif
## ML behavior appears to always round the grid size up to a power of 2
grid_n = 2 ^ nextpow2 (grid_n);
@@ -85,7 +92,7 @@
error ("fir2: grid size must be greater than half the filter order");
endif
- if isempty (ramp_n), ramp_n = fix (grid_n / 20); endif
+ if isempty (ramp_n), ramp_n = fix (grid_n / 25); endif
## Apply ramps to discontinuities
if (ramp_n > 0)
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