nex_wf

 nex_wf(filename, varname): Read waveform variable from a .nex file

 [adfreq, n, ts, nf, w] = nex_wf(filename, varname)

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

           
 OUTPUT:
   n - number of waveforms
   ts - array of waveform timestamps (in seconds)
   nf - number of data points in each waveform
   w - matrix of waveform a/d values [n nf] (in millivolts)

0001 function [adfreq, n, ts, nf, w] = nex_wf(filename, varname)
0002 % nex_wf(filename, varname): Read waveform variable from a .nex file
0003 %
0004 % [adfreq, n, ts, nf, w] = nex_wf(filename, varname)
0005 %
0006 % INPUT:
0007 %   filename - if empty string, will use File Open dialog
0008 %   varname - variable name
0009 %
0010 %
0011 % OUTPUT:
0012 %   n - number of waveforms
0013 %   ts - array of waveform timestamps (in seconds)
0014 %   nf - number of data points in each waveform
0015 %   w - matrix of waveform a/d values [n nf] (in millivolts)
0016 
0017 n = 0;
0018 adfreq = 0;
0019 ts = 0;
0020 nf = 0;
0021 w = 0;
0022 
0023 if(nargin ~= 2)
0024    disp('2 input arguments are required')
0025    return
0026 end
0027 
0028 if(ischar(filename) == 0)
0029    disp('input arguments should be character arrays')
0030    return
0031 end
0032 
0033 if(ischar(varname) == 0)
0034    disp('input arguments should be character arrays')
0035    return
0036 end
0037 
0038 if(isempty(filename))
0039    [fname, pathname] = uigetfile('*.nex', 'Select a Nex file');
0040     filename = strcat(pathname, fname);
0041 end
0042 
0043 fid = fopen(filename, 'r');
0044 if(fid == 0)
0045    return
0046 end
0047 
0048 disp(strcat('file = ', filename));
0049 magic = fread(fid, 1, 'int32');
0050 version = fread(fid, 1, 'int32');
0051 comment = fread(fid, 256, 'char');
0052 freq = fread(fid, 1, 'double');
0053 tbeg = fread(fid, 1, 'int32');
0054 tend = fread(fid, 1, 'int32');
0055 nvar = fread(fid, 1, 'int32');
0056 fseek(fid, 260, 'cof');
0057 name = zeros(1, 64);
0058 found = 0;
0059 for i=1:nvar
0060     type = fread(fid, 1, 'int32');
0061     var_version = fread(fid, 1, 'int32');
0062     name = fread(fid, [1 64], 'char');
0063     offset = fread(fid, 1, 'int32');
0064     nf = fread(fid, 1, 'int32');
0065     dummy = fread(fid, 32, 'char');
0066     adfreq = fread(fid, 1, 'double');
0067     adtomv = fread(fid, 1, 'double');
0068     n = fread(fid, 1, 'int32');
0069     name = char(name);
0070     name = deblank(name);
0071     k = strcmp(name, deblank(varname));
0072     if(k == 1)
0073         if type ~= 3
0074             disp(sprintf('%s is not a waveform variable', deblank(varname)));
0075             return;
0076         end
0077         found = 1;
0078         fseek(fid, offset, 'bof');
0079         ts = fread(fid, [1 nf], 'int32');
0080         w = fread(fid, [n nf], 'int16');
0081         break
0082     end
0083     dummy = fread(fid, 76, 'char');
0084 end
0085 
0086 fclose(fid);
0087 
0088 if found == 0
0089     disp('did not find variable in the file');
0090 else
0091     ts = ts/freq;
0092     w = w*adtomv;
0093     disp(strcat('number of waveforms = ', num2str(nf)));
0094 end