[R] LME Correlation Component using spectrum()?

[Keith Chamberlain]

Dear List-mates,

Is there a corStruct constructor already written to calculate the shape of
the spectral density for linear models using Fourier estimates (e.g. terms
for a linear model derived from the frequency domain)? I have data with a
long memory process but do not want to destroy it by taking n-differences
for a suitable corAR, or corARIMA object. 

Thank you,
KeithC.