## Copyright (C) 2000 Bill Lash ## ## This program is free software; you can redistribute it and/or modify ## it under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 2 of the License, or ## (at your option) any later version. ## ## This program is distributed in the hope that it will be useful, ## but WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ## GNU General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with this program; if not, write to the Free Software ## Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA ## Usage: b = unwrap(a{,tol{,dim}}) ## ## Unwrap radian phases by detecting jumps greater in magnitude ## than "tol" (default pi) and adding or subtracting 2*pi as ## appropriate. ## ## Unwrap will unwrap along the columns of "a" unless the row ## dimension of "a" is 1 or the "dim" argument is given with a ## value of 1, when it will unwrap along the row(s). ## Author: Bill Lash <lash@tellabs.com> function retval = unwrap(a,tol,dim) if ((nargin<1) || (nargin>3)) usage("unwrap(a,[tol,[dim]])") endif if (nargin < 3) if (rows(a)==1) dim = 1; #row vector, go along the row else dim = 2; # Otherwise go along the columns endif endif if (nargin < 2) tol = pi; endif if (tol == []) # if tol is not provided but dim is, handle it tol = pi; endif tol = abs(tol); # don't let anyone use a negative tol rng = 2*pi; ## Want to get data in a form so that we can unwrap each column if (dim == 1) ra = a.'; else ra = a; endif n = columns(ra); m = rows(ra); if (m == 1) # Handle case where we are trying to unwrap retval = a; # a scalar, or only have one sample in the return; # specified dimension endif ## take first order difference to see so that wraps will show up ## as large values, and the sign will show direction d = ; ## Find only the peaks, and multiply them by the range so that there ## are kronecker deltas at each wrap point multiplied by the range ## value p = rng * (((d > tol)>0) - ((d < -tol)>0)); ## Now need to "integrate" this so that the deltas become steps r = cumsum(p); ## Now add the "steps" to the original data and put output in the ## same shape as originally if (dim == 1) retval = (ra + r).'; else retval = (ra + r); endif endfunction %!shared r,w,tol %! r = ; #original vector %! w = r - 2*pi*floor((r+pi)/(2*pi)); #wrapped version value in [-pi,pi] %! tol = 1e3*eps; #maximum expected deviation %!assert(r, unwrap(w), tol) #unwrap single row %!assert(r', unwrap(w'), tol) #unwrap single column %!assert([r',r'], unwrap([w',w']), tol) #unwrap 2 columns %!assert([r;r], unwrap([w;w],,1), tol) #verify that dim works %!assert(r+10, unwrap(10+w), tol) #verify that r(1)>pi works %!assert(w', unwrap(w',[],1)) #unwrap col by rows should not change it %!assert(w, unwrap(w,[],2)) #unwrap row by cols should not change it %!assert([w;w], unwrap([w;w])) #unwrap 2 rows by cols should not change them %!## verify that setting tolerance too low will cause bad results. %!assert(any(abs(r - unwrap(w,0.8)) > 100)) %!error unwrap # not enough args %!error unwrap(1,2,3,4) # too many args

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