MATLAB Programming

6 Data Import and Export
m.Data(60).y(:,6) = [1 2 3 4];
% Generates an error.
Thus, if you map an entire file and then append to that file after constructing
the map, the appended data is not included in the mapped region. If you need
to modify the dimensions of data that you have mapped to a memmapfile
object, you must either modify the Format or Repeat properties for the object,
or reconstruct the object.
Examples. Two examples of statements that attempt to modify the
dimensions of a mapped Data field are shown here. These statements result
in an error.
The first example attempts to diminish the size of the array by removing a
row from the mapped array m.Data.
m.Data(5) = [];
The second example attempts to expand the size of a 50-row mapped array x
by adding another row to it:
m.Data(2).x(1:51,31) = 1:51;
Writing Matrices to a Mapped File
The syntax to use when writing to mapped memory can depend on what
format was used when you mapped memory to the file.
When Memory Is Mapped in Nonstructure Format. When you map a
file as a sequence of a single data type (e.g., a sequence of uint16), you can
use the following syntax to write matrix X to the file:
m.Data = X;
This statement is valid only if all of the following conditions are true:
• The file is mapped as a sequence of elements of the same data type, making
m.Data an array of a nonstructure type.
• The class of X is the same as the class of m.Data.
• The number of elements in X equals the number of elements in m.Data.
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