The dips at frequency 0 in slides 22 and 24 were consequences of the default subtraction of a mean. It is correct to subtract the mean, but then the component at frequency zero is necessarily zero and should be removed.
The parametric periodogram produced by fitting an AR(p) by AIC (slide 27) had a bug in the code, which has been corrected. The estimated spectrum is now a constant, corresponding to an AR(0) model.
The dips at frequency 0 in slides 22 and 24 were consequences of the default subtraction of a mean. It is correct to subtract the mean, but then the component at frequency zero is necessarily zero and should be removed.
The parametric periodogram produced by fitting an AR(p) by AIC (slide 27) had a bug in the code, which has been corrected. The estimated spectrum is now a constant, corresponding to an AR(0) model.