# Clarification on using spec.pgram in R

Does anyone understand how the argument "span" is used in spec.pgram in R? From the help menu, it provides the following examples:

spectrum(ldeaths)
spectrum(ldeaths, spans = c(3,5)) gives bandwidth= 0.241
spectrum(ldeaths, spans = c(5,7)) gives bandwidth= 0.363
spectrum(ldeaths, spans = 3)      gives bandwidth= 0.127

1. What do c(3,5) and c(3,7) or spans=3 represent?

2. How the bandwidths are calculated?

Thanks!

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When in doubt, read the help files.

help(spec.pgram)


spans: vector of odd integers giving the widths of modified Daniell smoothers to be used to smooth the periodogram.

bandwidth: The equivalent bandwidth of the kernel smoother as defined by Bloomfield (1976, page 201).

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 Thanks for the reference to Bloomfield's book. But could you please elucidate the difference between span=3 vs span c(3,3)? I read the help file, but I don't get it. – econ Apr 24 '12 at 7:17