The program rms.m calculates the root-mean-square value (RMS value) for an array of data.
The definition of RMS that is used in this program is the following:
suppose we have array of data Y (consisting of elements Y_1, Y_2, Y_3, etc...) which represent discrete values of the power spectrum versus frequency f. We divide frequency axis on small intervals of width df, each of such intervals contains one element of the array Y.
Then RMS = SQRT ( df * (Y_1 * Y_1) + df * (Y_2 * Y_2) + df * (Y_3 * Y_3) + ... ).