A Formant object represents formants as a function of time.
[ref: Praat help, https://www.fon.hum.uva.nl/praat/manual/Formant.html]
f$xmin
... start time (seconds)
f$xmax
... end time (seconds)
f$nx
... number of frames
f$dx
... time step = frame duration (seconds)
f$x1
... time associated with the first frame (seconds)
f$t
... vector of time instances associated with all frames
f$maxnFormants
... maximum number of formants in frame
f$frame[[1]]
to f$frame[[f$nx]]
... frames
f$frame[[1]]$intensity
... intensity of the frame
f$frame[[1]]$nFormants
... actual number of formants in this frame
f$frame[[1]]$frequency
... vector of formant frequencies (in Hz)
f$frame[[1]]$bandwidth
... vector of formant bandwidths (in Hz)