function [A,twt]=loadrd3(fname,varargin)
% loads an rd3 file... (requires the .rad file to be present)
% syntax: [A,twt]=loadrd3('prof4',[starttrace],[tracecount],[options]) 
%
% options: 'stack'... return the mean of the profile
%
% Aslak Grinsted 2002
%

% load details from .RAD file

fname=strrep(lower(fname),'.rd3','');

numargcount=size(varargin,2);
tracecount=inf;
starttrace=1;
stack=0;

l=1;
numargcount=size(varargin,2); %how many numeric arguments are there before the settings?
while (l<=size(varargin,2))
   a=varargin{l};
   if ischar(a)
      v=[];
      if (l<numargcount), numargcount=l-1; end
      %if ((l+1)<=size(varargin,2)), v=varargin{l+1}; end
      switch lower(a)
      case {'stack','s'}
          stack=1;
      end
   end
   l=l+1;
end
switch numargcount
case 2
    starttrace=varargin{1};
    tracecount=varargin{2};
end

infos=rd3info(fname,'scans','samples','timewindow');
sz=infos{2};
timewindow=infos{3};

twt=((1:sz)'-1)*timewindow*1e-9/sz;

%loads the rd3 file
fid=fopen([fname '.rd3'],'r');
if (starttrace>1)
   fseek(fid,(starttrace-1)*sz*2,0);
end

if (stack==0) 
    A=fread(fid,[sz tracecount],'short');
else
    blocksize=1+fix(1000000/sz); %number of traces to read at a time...
    
    A=zeros(sz,1);
    tracesread=0;
    while ((~feof(fid))&(tracesread<tracecount))
        B=fread(fid,[sz blocksize],'short');
        A=A+sum(B,2);
        tracesread=tracesread+size(B,2);
    end
    A=A/tracesread;
end
fclose(fid);
%A=reshape(A,sz,size(A,1)/sz);