# What does +(A>0) do?

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Mary on 11 Oct 2011
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!

David Young on 11 Oct 2011
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.
##### 2 CommentsShowHide 1 older comment
David Young on 11 Oct 2011
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form +() would continue to mean "convert to default numerical class", whereas double() would convert to a specific but outdated class.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!

Wolfgang Schwanghart on 11 Oct 2011
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 on 11 Oct 2011
Thanks -- this answer was also helpful and it's good to know which method is faster. I appreciate you taking the time to comment.

Fangjun Jiang on 11 Oct 2011
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)

Amey on 11 Oct 2011
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].