MATLAB Programming

6 Data Import and Export
Note While the MATLAB file I/O commands are modeled on the C language
I/O routines, in some ways their behavior is different. For example, the fread
function is vectorized; that is, it continues reading until it encounters a text
string or the end of file. These sections, and the MATLAB reference pages for
these functions, highlight any differences in behavior.
Opening Files
Before reading or writing a text or binary file, you must open it with the
fopen command.
fid = fopen('filename','permission')
Specifying the Permission String
The permission string specifies the kind of access to the file you require.
Possible permission strings include
• r for reading only
• w for writing only
• a for appending only
• r+ for both reading and writing
Note SystemssuchasMicrosoftWindowsthat distinguish between text and
binary files might require additional characters in the permission string, such
as 'rb' to open a binary file for reading.
Using the Returned File Identifier (fid)
If successful, fopen returns a nonnegative integer, called a file identifier
(fid). You pass this value as an argument to the other I/O functions to access
the open file. For example, this fopen statement opens the data file named
penny.dat for reading:
fid = fopen('penny.dat','r')
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