Clarification on using spec.pgram in R

Question

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!

Answer 1

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).