最近项目中需要使用MATLAB优秀的矩阵计算功能，然后再把矩阵保存到文件中，供其他语言的程序使用。这就需要把矩阵保存成文件格式，而不是mat形式。这里主要使用到了三种方法： by木子肖子

1. dlmwrite: 写ASCII编码的有分隔符的矩阵。

function dlmwrite(filename, m, varargin)
%DLMWRITE Write ASCII delimited file.
%
%   DLMWRITE('FILENAME',M) writes matrix M into FILENAME using ',' as the
%   delimiter to separate matrix elements.
%
%   DLMWRITE('FILENAME',M,'DLM') writes matrix M into FILENAME using the
%   character DLM as the delimiter.
%
%   DLMWRITE('FILENAME',M,'DLM',R,C) writes matrix M starting at
%   offset row R, and offset column C in the file.  R and C are zero-based,
%   so that R=C=0 specifies the first value in the file.
%
%   DLMWRITE('FILENAME',M,'ATTRIBUTE1','VALUE1','ATTRIBUTE2','VALUE2'...)
%   An alternative calling syntax that uses attribute value pairs for
%   specifying optional arguments to DLMWRITE. The order of the
%   attribute-value pairs does not matter, as long as an appropriate value
%   follows each attribute tag. 
%
%	DLMWRITE('FILENAME',M,'-append')  appends the matrix to the file.
%	without the flag, DLMWRITE overwrites any existing file.
%
%	DLMWRITE('FILENAME',M,'-append','ATTRIBUTE1','VALUE1',...)  
%	Is the same as the previous syntax, but accepts attribute value pairs,
%	as well as the '-append' flag.  The flag can be placed in the argument
%	list anywhere between attribute value pairs, but not between an
%	attribute and its value.
%
%   USER CONFIGURABLE OPTIONS
%
%   ATTRIBUTE : a quoted string defining an Attribute tag. The following 
%               attribute tags are valid -
%       'delimiter' =>  Delimiter string to be used in separating matrix
%                       elements.
%       'newline'   =>  'pc' Use CR/LF as line terminator
%                       'unix' Use LF as line terminator
%       'roffset'   =>  Zero-based offset, in rows, from the top of the
%                       destination file to where the data it to be
%                       written.                       
%       'coffset'   =>  Zero-based offset, in columns, from the left side
%                       of the destination file to where the data is to be
%                       written.
%       'precision' =>  Numeric precision to use in writing data to the
%                       file, as significant digits or a C-style format
%                       string, starting with '%', such as '%10.5f'.  Note
%                       that this uses the operating system standard
%                       library to truncate the number.
%
%
%   EXAMPLES:
%
%   DLMWRITE('abc.dat',M,'delimiter',';','roffset',5,'coffset',6,...
%   'precision',4) writes matrix M to row offset 5, column offset 6, in
%   file abc.dat using ; as the delimiter between matrix elements.  The
%   numeric precision is of the data is set to 4 significant decimal
%   digits.
%
%   DLMWRITE('example.dat',M,'-append') appends matrix M to the end of 
%   the file example.dat. By default append mode is off, i.e. DLMWRITE
%   overwrites the existing file.
%
%   DLMWRITE('data.dat',M,'delimiter','\t','precision',6) writes M to file
%   'data.dat' with elements delimited by the tab character, using a precision
%   of 6 significant digits.
%   
%   DLMWRITE('file.txt',M,'delimiter','\t','precision','%.6f') writes M
%   to file file.txt with elements delimited by the tab character, using a
%   precision of 6 decimal places. 
%
%   DLMWRITE('example2.dat',M,'newline','pc') writes M to file
%   example2.dat, using the conventional line terminator for the PC
%   platform.
%
%   See also DLMREAD, CSVWRITE, NUM2STR, SPRINTF.

%   Brian M. Bourgault 10/22/93
%   Modified: JP Barnard, 26 September 2002.
%             Michael Theriault, 6 November 2003 
%   Copyright 1984-2011 The MathWorks, Inc.
%-------------------------------------------------------------------------------

此方法按矩阵的行对数字进行格式调整，并一行一行的写入文件中，效率较慢，我测试了行10^7，列2的矩阵，用了880s。

2.num2str,然后再fprintf，先将矩阵转化为字符串，然后在fprinf写入矩阵。

%NUM2STR Convert numbers to a string.
%   T = NUM2STR(X) converts the matrix X into a string representation T
%   with about 4 digits and an exponent if required.  This is useful for
%   labeling plots with the TITLE, XLABEL, YLABEL, and TEXT commands.
%
%   T = NUM2STR(X,N) converts the matrix X into a string representation
%   with a maximum N digits of precision.  The default number of digits is
%   based on the magnitude of the elements of X.
%
%   T = NUM2STR(X,FORMAT) uses the format string FORMAT (see SPRINTF for
%   details).
%
%   Example 1:
%       num2str(randn(2,2),3) produces a string matrix such as
%
%        1.44    -0.755
%       0.325      1.37
%
%   Example 2:
%       num2str(rand(2,3) * 9999, '%10.5e\n') produces a string matrix
%       such as
%
%       8.14642e+03
%       1.26974e+03
%       6.32296e+03
%       9.05701e+03
%       9.13285e+03
%       9.75307e+02
%
%   See also INT2STR, SPRINTF, FPRINTF, MAT2STR.

%   Copyright 1984-2012 The MathWorks, Inc.
%------------------------------------------------------------------------------

3.fprintf函数

%FPRINTF Write formatted data to text file.
%   FPRINTF(FID, FORMAT, A, ...) applies the FORMAT to all elements of 
%   array A and any additional array arguments in column order, and writes
%   the data to a text file.  FID is an integer file identifier.  Obtain 
%   FID from FOPEN, or set it to 1 (for standard output, the screen) or 2
%   (standard error). FPRINTF uses the encoding scheme specified in the
%   call to FOPEN.
%
%   FPRINTF(FORMAT, A, ...) formats data and displays the results on the
%   screen.
%
%   COUNT = FPRINTF(...) returns the number of bytes that FPRINTF writes.
%
%   FORMAT is a string that describes the format of the output fields, and
%   can include combinations of the following:
%
%      * Conversion specifications, which include a % character, a
%        conversion character (such as d, i, o, u, x, f, e, g, c, or s),
%        and optional flags, width, and precision fields.  For more
%        details, type "doc fprintf" at the command prompt.
%
%      * Literal text to print.
%
%      * Escape characters, including:
%            \b     Backspace            ''   Single quotation mark
%            \f     Form feed            %%   Percent character
%            \n     New line             \\   Backslash
%            \r     Carriage return      \xN  Hexadecimal number N
%            \t     Horizontal tab       \N   Octal number N
%        For most cases, \n is sufficient for a single line break.
%        However, if you are creating a file for use with Microsoft
%        Notepad, specify a combination of \r\n to move to a new line.
%
%   Notes:
%
%   If you apply an integer or string conversion to a numeric value that
%   contains a fraction, MATLAB overrides the specified conversion, and
%   uses %e.
%
%   Numeric conversions print only the real component of complex numbers.
%
%   Example: Create a text file called exp.txt containing a short table of
%   the exponential function.
%
%       x = 0:.1:1;
%       y = [x; exp(x)];
%       fid = fopen('exp.txt','w');
%       fprintf(fid,'%6.2f  %12.8f\n',y);
%       fclose(fid);
%
%   Examine the contents of exp.txt:
%
%       type exp.txt
%
%   MATLAB returns:
%          0.00    1.00000000
%          0.10    1.10517092
%               ...
%          1.00    2.71828183
%
%   See also FOPEN, FCLOSE, FSCANF, FREAD, FWRITE, SPRINTF, DISP.

%   Copyright 1984-2009 The MathWorks, Inc.
%   Built-in function.

MATLAB保存矩阵的几种方法的比较