mhdrload_bis.m

function [header_mat, data_mat] = mhdrload_bis(file)
%MHDRLOAD_BIS Loads data from an ASCII file containing multiple text
% headers throughout the file.
% [header, data] = MHDRLOAD('filename.ext') reads a data file
% called 'filename.ext', which contains a text header.  There
% is no default extension; any extensions must be explicitly
% supplied.
%
% The first output, HEADER, is the header information, returned
% as a text array.
% The second output, DATA, is the data matrix.  This data matrix
% has the same dimensions as the data in the file, one row per
% line of ASCII data in the file.  If the data is not regularly
% spaced (i.e., each line of ASCII data does not contain the
% same number of points), the data is returned as a column
% vector.
%
% Limitations:  No lines of the text header can begin with
% a number.  The header must come before the data.
%
% MODIFIED from hdrload.m: Dec 20, 2002  Jeff Daniels, NSWCCD - ARD
%
% See also LOAD, SAVE, SPCONVERT, FSCANF, FPRINTF, STR2MAT, HDRLOAD.
% See also the IOFUN directory.
%
% EXAMPLE:
%   If example_data.txt is:
%   Recorded Data: 12/15/2001
%   header 1
%   rows = 2 cols = 2
%   12 23
%   34 21
%   header 2
%   rows = 3 cols = 3
%   19 73 13
%   33 32 47
%   34 12 68
%  
%   MHDRLOAD returns:
%     header(:,:,1) =
%    
%     Recorded Data: 12/15/2001
%     header 1                
%     rows = 2 cols = 2       
%    
%     header(:,:,2) =
%    
%     header 2                
%     rows = 3 cols = 3  
%
%     data(:,:,1) =
%    
%        12    23     0
%        34    21     0
%         0     0     0
%
%     data(:,:,2) =
%    
%        19    73    13
%        33    32    47
%        34    12    68

% check number and type of arguments
if nargin < 1
    error('Function requires one input argument');
elseif ~ischar(file)
    error('Input argument must be a string representing a filename');
end

% Open the file.  If this returns a -1, we did not open the file
% successfully.
fid = fopen(file);
if fid==-1
    error('File not found or permission denied.');
end

% Initialize loop variables
% We store the number of lines in the header, and the maximum length
% of any one line in the header.  These are used later in assigning
% the 'header' output variable.
no_lines = 0;
max_line = 0;

% We also store the number of columns in the data we read.  This way
% we can compute the size of the output based on the number of
% columns and the total number of data points.
ncols = 0;

% Finally, we initialize the data to [].
data = [];
j=1;

% Start processing.
line = fgetl(fid);
if ~ischar(line)
    disp('Warning: file contains no header and no data')
end;

while line~=-1,
    [data, ncols, errmsg, nxtindex] = sscanf(line, '%f');
    % One slight problem, pointed out by Peter VanderWal: If the first
    % character of the line is 'e', then this will scan as 0.00e+00.
    % We can trap this case specifically by using the 'next index'
    % output: in the case of a stripped 'e' the next index is one,
    % indicating zero characters read.  See the help entry for 'sscanf'
    % for more information on this output parameter.
    % We loop through the file one line at a time until we find some
    % data.  After that point we stop checking for header information.
    % This part of the program takes most of the processing time, because
    % fgetl is relatively slow (compared to fscanf, which we will use
    % later).
    while isempty(data)|(nxtindex==1)
        no_lines = no_lines+1;
        max_line = max([max_line, length(line)]);
        % Create unique variable to hold this line of text information.
        % Store the last-read line in this variable.
        eval(['line', num2str(no_lines), '=line;'])
        line = fgetl(fid);
        if ~ischar(line)
            disp('Warning: file contains no data')
        break
        end;
        [data, ncols, errmsg, nxtindex] = sscanf(line, '%f');
    end % while
   
    % Create header output from line information. The number of lines and
    % the maximum line length are stored explicitly, and each line is
    % stored in a unique variable using the 'eval' statement within the
    % loop. Note that, if we knew a priori that the headers were 10 lines
    % or less, we could use the STR2MAT function and save some work.
    % First, initialize the header to an array of spaces.
    header_mat(1:no_lines,1:max_line,j) = setstr(' '*ones(no_lines,max_line));
    for i = 1:no_lines,
        if length(eval(['line' num2str(i)])),
            varname = eval(['line' num2str(i)]);
        else
            varname = ['line',num2str(i)];
        end
        % Note that we only assign this line variable to a subset of this
        % row of the header array.  We thus ensure that the matrix sizes in
        % the assignment are equal.
        %eval(['header(i, 1:length(' varname ')) = ' varname ';']);
        header_mat(i,1:length(varname),j)=varname;
    end

    % Now that we have read in the first line of data, we can skip the
    % processing that stores header information, and just read in the
    % rest of the data.
    data = [data; fscanf(fid, '%f')];
    % Resize output data, based on the number of columns (as returned
    % from the sscanf of the first line of data) and the total number of
    % data elements. Since the data was read in row-wise, and MATLAB
    % stores data in columnwise format, we have to reverse the size
    % arguments and then transpose the data.  If we read in irregularly
    % spaced data, then the division we are about to do will not work.
    % Therefore, we will trap the error with an EVAL call; if the reshape
    % fails, we will just return the data as is.
    eval('data_mat(1:length(data)/ncols,1:ncols,j) = reshape(data,ncols, length(data)/ncols)'';', '')
    line = fgetl(fid);
    j=j+1;
    no_lines = 0;
end

fclose(fid);
% And we're done!

end