Partial spectra

     are the spectrum of the entire signal. The give no time specific information about the signal, but rather characterize the entire thing. For a stationary signal, this is quite approprate, as the spectra of an extended signal is very similar to that of short segments. If the heart rate was constant, and each pulse were of the same form, then this method would be appropriate for studying ECG's. However, neither of these conditions are true, and what we want to study is the variability of the heart rate. This means we want to look at the spectral parameters of the variations in the heart rate. For this, a spectra is more appropriate while the specimen is under the same physiological conditions.

Some examples of a partial spectrum are the standard FFT, and the sums of each frequency component of the EMD spectrogram.