sincinan.m

Univ. of Calgary CREWS的免费地震研究软件

function trout=sincinan(trin,t,tout,sizetable)
% SINCINAN: sinc function interpolation for signals with embedded nan's 
%
%  trout=sincinan(trin,t,tout,sizetable)
%  trout=sincinan(trin,t,tout)
% 
% SINCINAN performs 8 point sinc function interpolation using a 
% design for the approximate sinc function due to Dave Hale. It
% differs from SINCI in that it is specially modified to deal with
% the presence of NaN's in a sensible manner. SINCI will cause any
% trace portions containing NaN's to grow larger by the length of
% the interpolation function. SINCINAN avoids this by breaking the 
% input trace into live segments and interpolating each separatly.
% Each segment gets the same constant extrapolation end treatment as
% the trace as a whole; however this only affects interpolation sites
% falling within the live segment. Interpolation sites falling in NaN
% zones or outside the trace entirely will result in NaN's; however,
% these zones will not grow in size.
%
% trin= input trace
% t= time coordinate vector for trin. Trin must be regularly
%    sampled. SINCI uses on the first two point in t.
% tout= vector of times for which interpolated amplitudes are
%       desired
% trout= output trace. Contains the length(tout) interpolated 
%        amplitudes.
% sizetable= size of the sinc function table: [npts,nfuncs]
%     where npts = number of points on the sinc function and
%     nfuncs = number of uniquely optimized sinc functions. If dt is
%	  the input sample interval, then there will be a unique, optimized
%	  sinc function designed for interpolation every nfuncs'th of 
%	  dt.
%   ************* default = [8 25] *********
%
% by G.F. Margrave, November 1991
%	revised for NaN's January 1994
%
% NOTE: It is illegal for you to use this software for a purpose other
% than non-profit education or research UNLESS you are employed by a CREWES
% Project sponsor. By using this software, you are agreeing to the terms
% detailed in this software's Matlab source file.
 
% BEGIN TERMS OF USE LICENSE
%
% This SOFTWARE is maintained by the CREWES Project at the Department
% of Geology and Geophysics of the University of Calgary, Calgary,
% Alberta, Canada.  The copyright and ownership is jointly held by 
% its author (identified above) and the CREWES Project.  The CREWES 
% project may be contacted via email at:  [e-mail]
% 
% The term 'SOFTWARE' refers to the Matlab source code, translations to
% any other computer language, or object code
%
% Terms of use of this SOFTWARE
%
% 1) Use of this SOFTWARE by any for-profit commercial organization is
%    expressly forbidden unless said organization is a CREWES Project
%    Sponsor.
%
% 2) A CREWES Project sponsor may use this SOFTWARE under the terms of the 
%    CREWES Project Sponsorship agreement.
%
% 3) A student or employee of a non-profit educational institution may 
%    use this SOFTWARE subject to the following terms and conditions:
%    - this SOFTWARE is for teaching or research purposes only.
%    - this SOFTWARE may be distributed to other students or researchers 
%      provided that these license terms are included.
%    - reselling the SOFTWARE, or including it or any portion of it, in any
%      software that will be resold is expressly forbidden.
%    - transfering the SOFTWARE in any form to a commercial firm or any 
%      other for-profit organization is expressly forbidden.
%
% END TERMS OF USE LICENSE

if nargin<4, sizetable=[8,25];end

%convert to row vector
[rr,cc]=size(trin); trflag=0;
if(rr>1)
		trin=trin';
		t=t';
		tout=tout';
		trflag=1;
end

global SINC_TABLE

% see if table needs to be made
maketable=0;
[lsinc,ntable]=size(SINC_TABLE);
if( lsinc*ntable==0)
	maketable=1;
elseif( lsinc~=sizetable(1) | ntable~=sizetable(2) )
	maketable=1;
end

if(maketable)
		% Make the sinc function table
		 lsinc=sizetable(1);
		 ntable=sizetable(2);
		% lsinc should be an even integer
			frac=[0:ntable-1]/ntable;
		 SINC_TABLE=zeros(lsinc,ntable);
		 jmax=fix(ntable/2)+1;
		% the first half of the table is computed by least squares
		% while the second half is derived from the first by symmetry
			for j=1:jmax
					fmax=min([.066+.265*log(lsinc),1.0]);
					a=sinque(fmax*[0:lsinc-1]);
					b=fmax*([lsinc/2-1:-1:-lsinc/2]+frac(j)*ones(1,lsinc));
					c=sinque(b);
		   			SINC_TABLE(:,j)=toeplitz(a',a)\c';
		  	end
		  point=lsinc/2;
		  jtable=ntable;ktable=2;
		  while SINC_TABLE(point,jtable)==0.0
						SINC_TABLE(:,jtable)=flipud(SINC_TABLE(:,ktable));
						jtable=jtable-1;ktable=ktable+1;
		  end
end
% now interpolate with the tabulated coefficients
% first find the live and dead zones
	ilive=find(~isnan(trin));
	ind=find(diff(ilive)>1);
	zone_beg=[ilive(1) ilive(ind+1)];
	zone_end=[ilive(ind) ilive(length(ilive))];
	nzones=length(zone_beg);
	dtin=t(2)-t(1);
% now initialize the output trace with nans, then loop over the zones
% and interpolate traces that fall in them
	trout=nan*ones(size(tout));
	
	for k=1:nzones
	
		% get the input segment in this zone
		n1=round((t(zone_beg(k))-t(1))/dtin)+1;
		n2=round((t(zone_end(k))-t(1))/dtin)+1;
		trinzone=trin(n1:n2);
		tzone=t(n1:n2);
		%find the interpolation sites in this zone
			ii=between(t(zone_beg(k)),t(zone_end(k)),tout,2);
			troutzone=ones(size(ii));
		
		% changed the following on 8 October 93
			 if(ii(1)>0)
				pdata=(tout(ii)-tzone(1))/dtin+1;
				del=pdata-fix(pdata);
		% del now contains the fractional sample increment
		% for each interpolation site
		% compute row number in interpolation table
				ptable=1+round(ntable*del); 
		% compute pointer to input  data
				pdata=fix(pdata)+lsinc/2-1;
		% pad input data with end values
				trinzone=[trinzone(1)*ones(1,lsinc/2-1) trinzone ...
					trinzone(length(trinzone))*ones(1,lsinc/2)];
				ij=find(ptable==ntable+1);
				ptable(ij)=1*ones(1,length(ij));
				pdata(ij)=pdata(ij)+1;
		% finally interpolate by a vector dot product

				for k=1:length(ii)
						troutzone(k)=trinzone(pdata(k)-lsinc/2+1:pdata(k)+lsinc/2)...
									*SINC_TABLE(:,ptable(k));
				end

				trout(ii)=troutzone;
			end
  		
	  end

 if(trflag)
		trout=trout';
	end