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 ... option
  save('filename', ...)
  

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 ... option saves the workspace variables in the format specified by option

option Argument	Result: How Data is Stored
-append	The specified existed MAT-file, appended to the end
-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

Remarks

When saving in ASCII format, consider the following:

• Each variable to be saved must be either a two dimensional double array or a two dimensional character array. Saving a complex double array causes the imaginary part of the data to be lost, as MATLAB cannot load nonnumeric data ('i').
• In order to be able to read the file with the MATLAB load function, all of the variables must have the same number of columns. If you are using a program other than MATLAB to read the saved data this restriction can be relaxed.
• Each MATLAB character in a character array is converted to a floating point number equal to its internal ASCII code and written out as a floating point number string. There is no information in the save file that indicates whether the value was originally a number or a character.
• The values of all variables saved merge into a single variable that takes the name of the ASCII file (minus any extension). Therefore, it is advisable to save only one variable at a time.

With the v4 flag, you can only save data constructs that are compatible with versions of MATLAB 4. Therefore, you cannot save structures, cell arrays, multidimensional arrays, or objects. In addition, you must use filenames that are supported by MATLAB version 4.

save('filename', ...) is the function form of the syntax.

For more control over the format of the file, MATLAB provides other functions, as listed in See Also, below.

Algorithm

The binary formats used by save depend on the size and type of each array. Arrays with any noninteger entries and arrays with 10,000 or fewer elements are saved in floating-point formats requiring 8 bytes per real element. Arrays with all integer entries and more than 10,000 elements are saved in the formats shown, requiring fewer bytes per element.

Element Range	Bytes per Element
0 to 255	1
0 to 65535	2
-32767 to 32767	2
-231+1 to 231-1	4
other	8

External Interfaces to MATLAB provides details on reading and writing MAT-files from external C or Fortran programs. It is important to use recommended access methods, rather than rely upon the specific MAT-file format, which is likely to change in the future.

Examples

To save all variables from the workspace in binary MAT-file, test.mat, type

• save test.mat
  

To save variables p and q in binary MAT-file, test.mat, type

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

To save the variables vol and temp in ASCII format to a file named june10, type

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

See Also
diary, fprintf, fwrite, load, workspace

runtime

saveas