nex_marker

 nex_marker(filename, varname): Read a marker variable from a .nex file

 [n, nm, nl, ts, names, m] = nex_marker(filename, varname)

 INPUT:
   filename - if empty string, will use File Open dialog
   varname - variable name

           continuous (a/d) data come in fragments. Each fragment has a timestamp
           and a number of a/d data points. The timestamp corresponds to
           the time of recording of the first a/d value in this fragment.
           All the data values stored in the vector d. 
 OUTPUT:
   n - number of markers
   nm - number of fields in each marker
   nl - number of characters in each marker field
   ts - array of marker timestamps (in seconds)
   names - names of marker fields ([nm 64] character array)
   m - character array of marker values [n nl nm]

0001 function [n, nm, nl, ts, names, m] = nex_marker(filename, varname)
0002 % nex_marker(filename, varname): Read a marker variable from a .nex file
0003 %
0004 % [n, nm, nl, ts, names, m] = nex_marker(filename, varname)
0005 %
0006 % INPUT:
0007 %   filename - if empty string, will use File Open dialog
0008 %   varname - variable name
0009 %
0010 %           continuous (a/d) data come in fragments. Each fragment has a timestamp
0011 %           and a number of a/d data points. The timestamp corresponds to
0012 %           the time of recording of the first a/d value in this fragment.
0013 %           All the data values stored in the vector d.
0014 % OUTPUT:
0015 %   n - number of markers
0016 %   nm - number of fields in each marker
0017 %   nl - number of characters in each marker field
0018 %   ts - array of marker timestamps (in seconds)
0019 %   names - names of marker fields ([nm 64] character array)
0020 %   m - character array of marker values [n nl nm]
0021 
0022 n = 0;
0023 nm = 0;
0024 nl = 0;
0025 ts = 0;
0026 m = 0;
0027 names = 0;
0028 
0029 if(nargin ~= 2)
0030    disp('2 input arguments are required')
0031    return
0032 end
0033 
0034 if(ischar(filename) == 0)
0035    disp('input arguments should be character arrays')
0036    return
0037 end
0038 
0039 if(ischar(varname) == 0)
0040    disp('input arguments should be character arrays')
0041    return
0042 end
0043 
0044 if(isempty(filename))
0045    [fname, pathname] = uigetfile('*.nex', 'Select a Nex file');
0046     filename = strcat(pathname, fname);
0047 end
0048 
0049 fid = fopen(filename, 'r');
0050 if(fid == -1)
0051     disp('cannot open file');
0052    return
0053 end
0054 
0055 disp(strcat('file = ', filename));
0056 magic = fread(fid, 1, 'int32');
0057 version = fread(fid, 1, 'int32');
0058 comment = fread(fid, 256, 'char');
0059 freq = fread(fid, 1, 'double');
0060 tbeg = fread(fid, 1, 'int32');
0061 tend = fread(fid, 1, 'int32');
0062 nvar = fread(fid, 1, 'int32');
0063 fseek(fid, 260, 'cof');
0064 name = zeros(1, 64);
0065 found = 0;
0066 for i=1:nvar
0067     type = fread(fid, 1, 'int32');
0068     var_version = fread(fid, 1, 'int32');
0069     name = fread(fid, [1 64], 'char');
0070     offset = fread(fid, 1, 'int32');
0071     n = fread(fid, 1, 'int32');
0072     dummy = fread(fid, 32, 'char');
0073     adfreq = fread(fid, 1, 'double');
0074     adtomv = fread(fid, 1, 'double');
0075     npw = fread(fid, 1, 'int32');
0076     nm = fread(fid, 1, 'int32');
0077     nl = fread(fid, 1, 'int32');
0078     dummy = fread(fid, 68, 'char');
0079     name = char(name);
0080     name = deblank(name);
0081     k = strcmp(name, deblank(varname));
0082     if(k == 1)
0083         if type ~= 6
0084             disp(sprintf('%s is not a marker variable', deblank(varname)));
0085             return;
0086         end
0087         found = 1;
0088         fseek(fid, offset, 'bof');
0089         ts = fread(fid, [1 n], 'int32');
0090         names = zeros(1,64);
0091         m = zeros(n, nl, nm);
0092         for j=1:nm
0093             names(j, :) = fread(fid, [1 64], 'char');
0094             for p = 1:n
0095                 m(p, :, j) = fread(fid, [1 nl], 'char');
0096             end
0097         end
0098         break
0099     end
0100 end
0101 
0102 fclose(fid);
0103 
0104 if found == 0
0105     disp('did not find variable in the file');
0106 else
0107     names = char(names);
0108     m = char(m);
0109     ts = ts/freq;
0110     disp(strcat('number of markers = ', num2str(n)));
0111 end