Monthly mean relative sunspot numbers from 1749 to 1983. Collected at Swiss Federal Observatory, Zurich until 1960, then Tokyo Astronomical Observatory.
A time series of monthly data from 1749 to 1983.
Andrews, D. F. and Herzberg, A. M. (1985) Data: A Collection of Problems from Many Fields for the Student and Research Worker. New York: Springer-Verlag.
sunspot.month has a longer (and a bit different) series,
sunspot.year is a much shorter one. See there for
getting more current sunspot numbers.
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