MATLAB Programming

6 Data Import and Export
m = memmapfile('records.dat', ...
'Format', { ...
'uint16' [300 8] 'x'; ...
'double' [200 5] 'y' }, ...
'Repeat', 1, 'Writable', true);
m.Data.x = ones(300, 8, 'uint16');
When Memory Is Mapped in Nonscalar Structure Format. When you
map a file as a repeating sequence of multiple data types, you can use the
following syntax to write matrix X to the file, providing that k is a scalar index:
m.Data(k).field = X;
To do this, the following conditions must be true:
• Thefileismappedascontainingmultiple data types that can repeat,
making m.Data a nonscalar structure.
• k is a scalar index.
• The class of X isthesameastheclassofm.Data(k).field.
• The number of elements in X equals that of m.Data(k).field.
This example maps a file as a matrix of type uint16 followed by a matrix of
type double that repeat 20 times, and then uses the syntax shown above
to write a matrix to the file.
m = memmapfile('records.dat', ...
'Format', { ...
'uint16' [25 8] 'x'; ...
'double' [15 5] 'y' }, ...
'Repeat', 20, 'Writable', true);
d = m.Data;
d(12).x = ones(25,8,'uint16');
You can write to specific elements of field x as shown here:
d(12).x(3:5,1:end) = uint16(500);
d(12).x(3:5,1:end)
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