[Octave-cvsupdate] SF.net SVN: octave:[10874] trunk/octave-forge/main/signal/inst/fir2.m

[<mtm...@us...>]

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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