hilbertspec {EMD} | R Documentation |
This function calculates the amplitude and instantaneous frequency using Hilbert transform.
hilbertspec(xt, tt=NULL, central=FALSE)
xt |
matrix of multiple signals. Each column represents a signal. |
tt |
observation index or time index |
central |
If central=TRUE, use central difference method to calculate the instantaneous frequency |
This function calculates the amplitude and instantaneous frequency using Hilbert transform.
amplitude |
matrix of amplitudes for multiple signals |
instantfreq |
matrix of instantaneous frequencies for multiple signals |
energy |
cumulative energy of multiple signals |
Huang, N. E., Shen, Z., Long, S. R., Wu, M. L. Shih, H. H., Zheng, Q., Yen, N. C., Tung, C. C. and Liu, H. H. (1998) The empirical mode decomposition and Hilbert spectrum for nonlinear and nonstationary time series analysis. Proceedings of the Royal Society London A, 454, 903–995.
Dasios, A., Astin, T. R. and McCann C. (2001) Compressional-wave Q estimation from full-waveform sonic data. Geophysical Prospecting, 49, 353–373.
tt <- seq(0, 0.1, length = 2001)[1:2000]
f1 <- 1776; f2 <- 1000
xt <- sin(2*pi*f1*tt) * (tt <= 0.033 | tt >= 0.067) + sin(2*pi*f2*tt)
### Before treating intermittence
interm1 <- emd(xt, tt, boundary="wave", max.imf=2, plot.imf=FALSE)
### After treating intermittence
interm2 <- emd(xt, tt, boundary="wave", max.imf=2, plot.imf=FALSE,
interm=0.0007)
par(mfrow=c(2,1), mar=c(2,2,2,1))
test1 <- hilbertspec(interm1$imf)
spectrogram(test1$amplitude[,1], test1$instantfreq[,1])
test2 <- hilbertspec(interm2$imf, tt=tt)
spectrogram(test2$amplitude[,1], test2$instantfreq[,1])