In Matlab
, what exactly does the expression M()
do where M
is a matrix?
>> M = magic(3);
>> M()
ans =
8 1 6
3 5 7
4 9 2
Is the expression isequaln(M, M())
true under all circumstances? Is M()
simply a copy of M
, or an identical expression, or is there any context where referring to M()
means something else than referring to M
? Maybe in the case of operator overloading?
example. TF = isempty( A ) returns logical 1 ( true ) if A is empty, and logical 0 ( false ) otherwise. An empty array, table, or timetable has at least one dimension with length 0, such as 0-by-0 or 0-by-5.
An empty matrix has no rows and no columns. A matrix that contains missing values has at least one row and column, as does a matrix that contains zeros. The J function in SAS/IML software creates a matrix that has a specified number of rows and columns and fills the matrix with a constant value.
Strings always contain the empty string as a substring.
Like all MATLAB® arrays, cell arrays are rectangular, with the same number of cells in each row. myCell is a 2-by-3 cell array. You also can use the {} operator to create an empty 0-by-0 cell array. To add values to a cell array over time or in a loop, create an empty N -dimensional array using the cell function.
Besides the fact the it would give the default operation on some function, such as rand()
, and easter eggs such as imagesc()
and spy()
(this will work also without the ()
) , it seems to be a more efficient way to access whole arrays as long as their dimensionality is below 5 (as @Rody Oldenhuis spotted) . For example:
a=rand(2^12);
tic
for j=1:1e5
a ;
end
toc
tic
for j=1:1e5
a(:) ;
end
toc
tic
for j=1:1e5
a() ;
end
toc
yield:
Elapsed time is 0.047250 seconds.
Elapsed time is 0.022260 seconds.
Elapsed time is 0.011925 seconds.
However, for assignments there's very little difference between a1=a
vs a1=a()
, where the latter is slower by 1.5%...
Perhaps this thread will answer some of your question regarding operator overloading.
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