Vectorizing inside a loop

I am trying to implement something like this

for i=1:n
matrix(i:n:end,4:6)=y(i,:)-matrix(i,1:3);
end

I was under the impression that vectorizing would allow me to eliminate the need for another loop but I receive 'Subscripted assignment dimension mismatch' when I attempt to evaluate this. I believe it is because it is not assigning it on a per row basis as I had hoped.

Is it at all possible to accomplish this without adding more loops?

[ChristianW]

What is size(y) and size(matrix)? Which value has n? What are you trying with i:n:end?

The right part of your equation is a 1x3 vector and the left part is a mx3 matrix, thats why dimensions mismatch.

[Avery]

y is an n by 3 matrix. n changes, hence it being a variable, as do the size of y and matrix. I understand that the left is a matrix and the right is a vector, but my understanding of vectorization leads me to believe that I can replace a loop in this way.

[ChristianW]

Show your working double loop.

Answer 1

[Babak]

The problem with

 matrix(i:n:end,4:6)=y(i,:)-matrix(i,1:3);

is that the first index i:n:end is a vector and does not correspond to 1 element. On the other hand, on the righe side, the index i is a sinle element which chooses the row with index i.

You need to change i:n:end to a proper single index accordign to what you want to write to. If you give a numerical example, maybe I can figure what you really want to do.