MATLAB Programming

Using Memory Efficiently
S2(1:100,1:50).G
S2(1:100,1:50).B
Thus, even though S1 and S2 contain the same amount of data, S1 uses
significantly less space in memory. Not only is less memory required, but
there is a corresponding speed benefit to using the S1 format as well.
Memory Usage Reported By the whos Function. The whos function
displays the amount of memory consumed by any variable. For reasons of
simplicity, whos reports only the memory used to store the actual data. It does
not report storage for the variable itself or the array header.
Function Arguments
MATLAB handles arguments passed in function calls in a similar way. When
you pass a variable to a function, you are actually passing a pointer to the
data that the variable represents. As long as the input data is not modified
by the function being called, the variable in the calling function and the
variable in the called function point to the same location in memory. If the
called function modifies the value of the input data, then MATLAB makes
a copy of the original array in a new location in memory, updates that copy
with the modified value, and points the input variable in the called function
to this new array.
In the example below, function myfun modifies the value of the array passed
into it. MATLAB makes a copy in memory of the array pointed to by A, sets
variable X as a pointer to this new array, and then sets one row of X to zero.
The array referenced by A remains unchanged:
A = magic(500);
myfun(A);
function myfun(X)
X(400,:) = 0;
If the calling function needs the modified value of the array it passed to
myfun, you will need to return the updated array as an output of the called
function, as shown here for variable A:
A = magic(500);
A = myfun(A);
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