beginner questions about symbols used in formula

sample./(sqrtvar(:,ones(n,1))

What does the full stop and the colon do in the above formula?

Answer 1

[Amit]

The fullstop (.) operator is for element-wise operation. For example:

A = [1 2 3 4]; 
B = [5 6 7 8];

AS you can see that A and B both are 1X4 matrices and normal matrix multiplication can not be done. However, lets say you want an output C as [1*5 2*6 3*7 4*8] (i.e. multiply each element with the corresponding element), then you can do

C = A.*B;

The colon operator (:) is a way to write 1:end. In the example here, to access all the element of A, you can write:

A(1,1:4)
A(1,1:end)
or A(1,:)

All 3 a legit way to do this and will give same result.

For more: http://www.mathworks.com/help/matlab/ref/times.html

http://www.mathworks.com/help/matlab/ref/colon.html