what is the equivalent matlab function for the operator || || ?

I am having an expression r=||x-Ab|| which I have to convert it into a matlab code.But i have no idea what is this || || operator.can anyone tell me what does it mean and what is the equivalent matlab fuction for it.

[Geoff Hayes]

mari - please provide some context for this operator. What does it mean to you? What goes between the two pairs of vertical bars?

Answer 1

[Andrew Newell]

You're probably referring to the matrix norm, which is a generalization of the idea of "distance". The equivalent MATLAB function is norm. If there is no subscript on your operator symbol, it probably represents the 2-norm, which is the default for the MATLAB function. For your example, you could write

r = norm(x-A*b);

See also Operator norm.