power_fftscope with less than 1/60 seconds of data

Good day all,

I have captured data from an oscilloscope (tektronix). I have pre-processed the data to bring it into matlab with all positive time and the 'structure with time' format.

Because my max time is .01, I fake a 60hz signal by repeating the last value of my signal and concatenating a value of .0167 (>1/60). I then run the following process:

signal_thd = power_fftscope(signal);
signal_thd.fundamental = new_fudnamental;
signal_thd.time = signal_thd.time(1:end-1); % this removes my added t=.0167
signal_thd.signal.value = signal_thd.signals.values(1:end-1); % this removes my repeated last value
signal_thd = power_fftscope(signal_thd);

This seems to work well enough in that I get expected numbers for the harmonics I saw in my scope.

The question is this two part: 1) Is there a more effective way do the above procedure, ie preload the frequency? 2) Is there a way to determine subharmonics?

Thank you very much for your time, Byron