nex_cont

 nex_cont(filename, varname): Read continuous variable from a .nex file

 [adfreq, n, ts, fn, d] = nex_cont(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 - total number of data points 
   ts - array of fragment timestamps (one timestamp for fragment, in seconds)
   fn - number of data points in each fragment
   d - array of a/d values (in millivolts)

0001 function [adfreq, n, ts, fn, d] = nex_cont(filename, varname)
0002 % nex_cont(filename, varname): Read continuous variable from a .nex file
0003 %
0004 % [adfreq, n, ts, fn, d] = nex_cont(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 - total number of data points
0016 %   ts - array of fragment timestamps (one timestamp for fragment, in seconds)
0017 %   fn - number of data points in each fragment
0018 %   d - array of a/d values (in millivolts)
0019 
0020 n = 0;
0021 adfreq = 0;
0022 ts = 0;
0023 fn = 0;
0024 d = 0;
0025 
0026 if(nargin ~= 2)
0027    disp('2 input arguments are required')
0028    return
0029 end
0030 
0031 if(ischar(filename) == 0)
0032    disp('input arguments should be character arrays')
0033    return
0034 end
0035 
0036 if(ischar(varname) == 0)
0037    disp('input arguments should be character arrays')
0038    return
0039 end
0040 
0041 if(isempty(filename))
0042    [fname, pathname] = uigetfile('*.nex', 'Select a Nex file');
0043     filename = strcat(pathname, fname);
0044 end
0045 
0046 fid = fopen(filename, 'r');
0047 if(fid == 0)
0048    return
0049 end
0050 
0051 disp(strcat('file = ', filename));
0052 magic = fread(fid, 1, 'int32');
0053 version = fread(fid, 1, 'int32');
0054 comment = fread(fid, 256, 'char');
0055 freq = fread(fid, 1, 'double');
0056 tbeg = fread(fid, 1, 'int32');
0057 tend = fread(fid, 1, 'int32');
0058 nvar = fread(fid, 1, 'int32');
0059 fseek(fid, 260, 'cof');
0060 name = zeros(1, 64);
0061 found = 0;
0062 for i=1:nvar
0063     type = fread(fid, 1, 'int32');
0064     var_version = fread(fid, 1, 'int32');
0065     name = fread(fid, [1 64], 'char');
0066     offset = fread(fid, 1, 'int32');
0067     nf = fread(fid, 1, 'int32');
0068     dummy = fread(fid, 32, 'char');
0069     adfreq = fread(fid, 1, 'double');
0070     adtomv = fread(fid, 1, 'double');
0071     n = fread(fid, 1, 'int32');
0072     name = char(name);
0073     name = deblank(name);
0074     k = strcmp(name, deblank(varname));
0075     if(k == 1)
0076         if type ~= 5
0077             disp(sprintf('%s is not a continuous variable', deblank(varname)));
0078             return;
0079         end
0080         found = 1;
0081         fseek(fid, offset, 'bof');
0082         ts = fread(fid, [1 nf], 'int32');
0083         fn = fread(fid, [1 nf], 'int32');
0084         d = fread(fid, [1 n], 'int16');
0085         break
0086     end
0087     dummy = fread(fid, 76, 'char');
0088 end
0089 
0090 fclose(fid);
0091 
0092 if found == 0
0093     disp('did not find variable in the file');
0094 else
0095     ts = ts/freq;
0096     d = d*adtomv;
0097     fn(nf+1) = n;
0098     fn = diff(fn);
0099     disp(strcat('number of data points = ', num2str(n)));
0100 end