MATLAB Function Reference

save

Save workspace variables on disk

Graphical Interface

As an alternative to the save function, select Save Workspace As from the File menu in the MATLAB desktop, or use the Workspace browser.

Syntax

• save
  save('filename')
  save('filename', 'var1', 'var2', ...)
  save('filename', '-struct', 's')
  save('filename', '-struct', 's', 'f1', 'f2', ...)
  save('-regexp', expr1, expr2, ...)
  save('..., 'format')
  save filename var1 var2 ...
  

Description

save by itself stores all workspace variables in a binary format in the current directory in a file named matlab.mat. Retrieve the data with load. MAT-files are double-precision, binary, MATLAB format files. They can be created on one machine and later read by MATLAB on another machine with a different floating-point format, retaining as much accuracy and range as the different formats allow. They can also be manipulated by other programs external to MATLAB.

save('filename') stores all workspace variables in the current directory in filename.mat. To save to another directory, use the full pathname for the filename. If filename is the special string stdio, the save command sends the data as standard output.

save('filename', 'var1', 'var2', ...) saves only the specified workspace variables in filename.mat. Use the * wildcard to save only those variables that match the specified pattern. For example, save('A*') saves all variables that start with A.

save('filename', '-struct', 's') saves all fields of the scalar structure s as individual variables within the file filename.

save('filename', '-struct', 's', 'f1', 'f2', ...) saves as individual variables only those structure fields specified (s.f1, s.f2, ...).

save('-regexp', expr1, expr2, ...) saves those variables that match any of the regular expressions expr1, expr2, etc.

save(..., 'format') enables you to make use of other data formats available with the save function. See the following table.

Format	How Data Is Stored
-append	The specified existing MAT-file, appended to the end. See Remarks, below.
-ascii	8-digit ASCII format
-ascii -double	16-digit ASCII format
-ascii -tabs	Delimits with tabs
-ascii -double -tabs	16-digit ASCII format, tab delimited
-mat	Binary MAT-file form (default)
-v4	A format that MATLAB Version 4 can open
-v6	A format that MATLAB Version 6 and earlier can open

save filename var1 var2 ... is the command form of the syntax.

Remarks

By default, MATLAB compresses the data it saves to MAT-files. MATLAB also uses Unicode character encoding when saving character data. Specify the -v6 option if you want to disable both of these features for a particular save operation. If you save data to a MAT-file that you intend to load using MATLAB Version 6 or earlier, then you must specify the -v6 option when saving.

To override the compression and Unicode setting for all of your MATLAB sessions, use the Preferences dialog box. Open the Preferences dialog and select General and then MAT-Files. To disable data compression and Unicode encoding, click Ensure backward compatibility (-v6). To turn these features back on, click Use default features (Unicode and compression). See General Preferences for MATLAB in the Desktop Tools and Development Environment documentation for more information.

For information on any of the following topics related to saving to MAT-files, see Exporting Data to MAT-Files in the "MATLAB Programming" documentation:

• Appending variables to an existing MAT-file
• Compressing data in the MAT-file
• Saving in ASCII format
• Saving in MATLAB Version 4 format
• Saving with Unicode character encoding
• Data storage requirements
• Saving from external programs

Examples

Example 1

Save all variables from the workspace in binary MAT-file test.mat:

• save test.mat
  

Example 2

Save variables p and q in binary MAT-file test.mat:

• savefile = 'test.mat';
  p = rand(1, 10);
  q = ones(10);
  save(savefile, 'p', 'q')
  

Example 3

Save the variables vol and temp in ASCII format to a file named june10:

• save('d:\mymfiles\june10','vol','temp','-ASCII')
  

Example 4

Save the fields of structure s1 as individual variables rather than as an entire structure.

• s1.a = 12.7;  s1.b = {'abc', [4 5; 6 7]};  s1.c = 'Hello!';
  save newstruct.mat -struct s1;
  clear
  

Check what was saved to newstruct.mat:

• whos -file newstruct.mat
    Name      Size                   Bytes  Class
  
    a         1x1                        8  double array
    b         1x2                      158  cell array
    c         1x6                       12  char array
  
  Grand total is 16 elements using 178 bytes
  

Read only the b field into the MATLAB workspace.

• str = load('newstruct.mat', 'b')
  str = 
      b: {'abc'  [2x2 double]}
  

Example 5

Using regular expressions, save in MAT-file mydata.mat those variables with names that begin with Mon, Tue, or Wed:

• save('mydata', '-regexp', '^Mon|^Tue|^Wed');
  

Here is another way of doing the same thing. In this case, there are three separate expression arguments:

• save('mydata', '-regexp', '^Mon', '^Tue', '^Wed');
  

Example 6

Save a 3000-by-3000 matrix uncompressed to file c1.mat, and compressed to file c2.mat. The compressed file uses about one quarter the disk space required to store the uncompressed data:

• x = ones(3000);
  y = uint32(rand(3000) * 100);
  
  save c1 x y
  save c2 x y -compress
  
  d1 = dir('c1.mat');
  d2 = dir('c2.mat');
  
  d1.bytes
  ans =
      45000240          % Size of the uncompressed data
  d2.bytes
  ans =
      11985634          % Size of the compressed data
  
  d2.bytes/d1.bytes
  ans =
      0.2663            % Ratio of compressed to uncompressed
  

Example 7

This example is similar to the last one, except that it saves one variable uncompressed, and then a second variable compressed to the same MAT-file. It then loads this data back into the MATLAB workspace:

• x = ones(3000);
  y = uint32(rand(3000) * 100);
  
  save c1 x;
  save c1 y -compress -append;
  
  d = dir('c1.mat');
  d.bytes
  ans =
      20952950
  
  clear
  load c1
  whos
    Name      Size                   Bytes  Class
  
    x      3000x3000              72000000  double array
    y      3000x3000              36000000  uint32 array
  
  Grand total is 18000000 elements using 108000000 bytes
  

See Also

load, clear, diary, fprintf, fwrite, genvarname, who, workspace

run

saveas

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