Binary mask operation: vector into nonzero part of mask in 1 statement?

I have a logical matrix MASK and a vector VEC with real numbers (uint8 mostly). nnz(MASK) equals length(VEC).

I create a new matrix NEW where the logical 1's in MASK are replaced by the values in VEC--in sequential order:

 NEW = MASK;
 NEW(NEW>0) = VEC;

Can I do this with 1 statement? Because in practice I want to replace NEW with VEC since I dont need VEC anymore after the operation, and don't want to pile up variables. MASK should remain untouched.

Thanks

Answer 1

[Image Analyst]

I think you can just do:

VEC(~MASK) = 0;

I think this will do the same thing - set VEC to zero where MASK is false, and VEC stays VEC where MASK is true.

By the way, you can use clear('variableName') to get rid of variables you don't need anymore.

[Jurgen]

Im afraid that doesn't work since MASK has more elements than VEC. If it helps, a concrete example is a circular roi in a 2D mask. The contents of the vector should replace the circle only, and thus contain less values than mask. Padding the vector would involve more statements / variables too, so that's no improvement either.

I was thinking of making a function that columnates MASK, applies elementwise sequential multiplication if it encounters a 1 in MASK, then reshapes the column back to MASK. But I want to avoid re-inventing the wheel, especially if my wheel is slower...

[Image Analyst]

Please give small examples for vec and mask, something like:

mask = false(5,5);
mask(2:4, 2:4) = true
vec = randi(255, [3,3])

and give what you want vec to look like when all is said and done.

[Image Analyst]

It looks like in your code demo that vec will need to get resized, so no, there's no way to do it in a single assignment. Use clear('VEC') to get rid of VEC after you've created NEW.

[Jurgen]

Thanks, in the end I just made a function that takes the mask and vector and spits out a substituted image. If you cant beat em, join em :)