RMS, as in root-mean-square? That should simply return the average amplitude of a time-varying signal. You should be able to call rms(data) in Matlab, assuming that "data" is a 1D array taken at a constant sample rate. It will spit out a single number.
If you find the RMS value of a set of values that are all positive values, it will return the same as mean() or average(). RMS can be thought of like the average function, but it looks at the signal's magnitude, regardless of if it's positive or negative.
To calculate RMS manually, take the square root of the mean (average) of the square of each value. So, if you have x1, x2, x3, x4...
Square each term: x1^2, x2^2, x3^2, x4^2... xn^2
Take the average: (x1^2 + x2^2 + x3^2 + x4^2 +... +xn^2) / n
Take the square root: sqrt( (x1^2 + x2^2 + x3^2 + x4^2 +... +xn^2) / n ) = RMS value
If RMS stands for something else in this case, then I can't help you :wink: