Root mean square

Syntax: | `s = RMS(x)` `s = RMS(w,x)`

The `RMS` function only accepts one or two vector arguments. If only one vector is entered, the function returns the root-mean-square of that vector's data. If two vectors are entered, the first vector holds the weights and the second vector holds the data. The result is always a scalar value.

Suppose that x is a vector with N elements.

A weight vector, w, may be entered as the first argument. The length of w is assumed to also be N. If no weights are entered, let default to `1`, for . Define the total weight:

The root-mean-square, , is defined by