What does +(A>0) do?

I'm an experienced Matlab user, but I came across a line of code that I don't understand:

A = +(A>0)

I know that the A>0 will find indices for values of A greater than zero, but any thoughts on what the +() does?

Thanks!

Answer 1

[David Young]

Looks like someone is forcing the class of A to be double rather than logical.

A = double(A>0)

would have the same effect but would be much clearer, and therefore preferable.

[Fangjun Jiang]

That's a good argument, in terms of changing the data type of A.

[David Young]

Though I suppose if MATLAB ever changed its default numerical class from double to something else, the form +() would continue to mean "convert to default numerical class", whereas double() would convert to a specific but outdated class. This is, however, an unlikely scenario!

Answer 2

[Wolfgang Schwanghart]

I often do this to convert a logical matrix to double. However, I just tried and realized that this is slower than A = double(A>0).

A = rand(4000,4000)>0.5;
>> tic; B = double(A); toc
Elapsed time is 0.041147 seconds.
>> tic; B = +(A); toc
Elapsed time is 0.053846 seconds.

Again, I have learned something here.

[Mary]

Thanks -- this answer was also helpful and it's good to know which method is faster. I appreciate you taking the time to comment.

Answer 3

[Fangjun Jiang]

The "+" doesn't mean anything here. Probably somebody with C++ experience wrote it. You can try this example:

A=rand(3)-0.5;
A=+(A>0);

Think of it as

A=0+(A>0)

Answer 4

[Amey]

In the matrix A, it indicates which values are greater than zero. For example: A = [-3 -1 0 9 4 3 2]; The output of the command b = +(A>0) is: b = [0 0 0 1 1 1 1]

Below is another example for the operation. Consider the same matrix A = [-3 -1 0 9 4 3 2]; The output of the command b = +(A>-2) is: b = [0 1 1 1 1 1 1].