Spectral Density Functions for Long-Memory Processes
Draws the spectral density functions (SDFs) for standard long-memory processes including fractional difference (FD), seasonal persistent (SP), and seasonal fractional difference (SFD) processes.
fdp.sdf(freq, d, sigma2 = 1) spp.sdf(freq, d, fG, sigma2 = 1) spp2.sdf(freq, d1, f1, d2, f2, sigma2 = 1) sfd.sdf(freq, s, d, sigma2 = 1)
freq |
vector of frequencies, normally from 0 to 0.5 |
d,d1,d2 |
fractional difference parameter |
fG,f1,f2 |
Gegenbauer frequency |
s |
seasonal parameter |
sigma2 |
innovations variance |
The power spectrum from an FD, SP or SFD process.
Brandon Whitcher
dB <- function(x) 10 * log10(x) fdp.main <- expression(paste("FD", group("(",d==0.4,")"))) sfd.main <- expression(paste("SFD", group("(",list(s==12, d==0.4),")"))) spp.main <- expression(paste("SPP", group("(",list(delta==0.4, f[G]==1/12),")"))) freq <- 0:512/1024 par(mfrow=c(2,2), mar=c(5-1,4,4-1,2), col.main="darkred") plot(freq, dB(fdp.sdf(freq, .4)), type="l", xlab="frequency", ylab="spectrum (dB)", main=fdp.main) plot(freq, dB(spp.sdf(freq, .4, 1/12)), type="l", xlab="frequency", ylab="spectrum (dB)", font.main=1, main=spp.main) plot(freq, dB(sfd.sdf(freq, 12, .4)), type="l", xlab="frequency", ylab="spectrum (dB)", main=sfd.main)
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