MATLAB Programming

6 Data Import and Export
Loading Binary Data
MAT-files are double-precision binary MATLAB format files created by the
save function and readable by the load function. 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.
MAT-filescancontaindatainanuncompressedoracompressedform,orboth.
MATLAB knows which variables in the file have been compressed by looking
at a tag that it attaches to each variable during the save operation. When
loading data from a MAT-file into the workspace, MATLAB automatically
handles the decompression of the appropriate data.
The External Interface libraries contain C- and Fortran-callable routines to
read and write MAT-files from external programs.
Loading ASCII Data
ASCII files must be organized as a rectangular table of numbers, with each
number in a row separated by a blank, comma, or tab character, and with
an equal number of elements in each row. MATLAB generates an error if
the number of values differs between any two rows. ASCII files can contain
MATLAB comments (lines that begin with %).
MATLAB returns all the data in the file as a single two-dimensional array
of type double. The number of rows in the array is equal to the number of
lines in the file, and the number of columns is equal to the number of values
on a line.
In the workspace, MATLAB assigns the array to a variable named after the
file being loaded (minus any file extension). For example, the command
load mydata.dat
reads all of the data from mydata.dat into the MATLAB workspace as a single
array, and assigns it to a variable called mydata. Innamingthevariable,load
precedes any leading underscores or digits in filename with an X and replaces
any other nonalphabetic characters with underscores.
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