dot in an expression

Hi guys. What does the dot in sinc(x) = sin(x)./x do? Remove a singularity or what?

Answer 1

[David Fletcher]

Element by element division

[Robert Bag]

but why do I not need in for instance sin(x)? isnt it already understood that this is not a matrix?

[David Fletcher]

It could be a matrix - if you applied the sin function and x was a matrix it would apply sin(x) to each value in the matrix, but the way sin is applied is not fundamentally different whether x is a scaler, a vector, or a matrix, whereas x.*y is a fundamentally different method of application than x*y (element by element multiplication as opposed to matrix multiplication). In your example the dot indicates element by element division as opposed to matrix right division which is used to solve linear equations

[Robert Bag]

Thanks a lot. But why do i especially need it for sin(x)/x? I get an error when i but it without a dot. I thought it had stg to do with that it is not defined on x = 0?

[Robert Bag]

Ok read now.thnx

[Adam Danz]

Compare the following

x = magic(3)

x = 3×3

8 1 6 3 5 7 4 9 2

sin(x)/x    % matrix division

ans = 3×3

0.0997 -0.1770 0.1807 0.0666 0.0824 -0.1597 -0.1543 0.2902 -0.0983

sin(x)./x   % element-wise division

ans = 3×3

0.1237 0.8415 -0.0466 0.0470 -0.1918 0.0939 -0.1892 0.0458 0.4546

Additional reference: https://www.mathworks.com/help/matlab/matlab_prog/array-vs-matrix-operations.html