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% File src/library/datasets/man/sunspot.month.Rd
% Part of the R package, https://www.R-project.org
% Copyright 1995-2024 R Core Team
% Distributed under GPL 2 or later

\name{sunspot.month}
\title{Monthly Sunspot Data, from 1749 to "Present"}
\docType{data}
\alias{sunspot.m2014}
\alias{sunspot.month}
\description{
  Monthly numbers of sunspots, as from the World Data Center, aka
  \abbr{SIDC}.  \code{sunspot.month} is the version of the data that will
  occasionally be updated when new counts become available (or the numbers
  are \I{recalibrated}). Note that around 2014--2015 there has been an
  international effort to \I{recalibrate} the sunspots numbers; since \R 4.5.0
  (2025), the \I{recalibrated} series is used.
  \cr % ~/R/MM/MISC/read-sunspots.R
  The version in (too long) use from 2014 to 2024 is provided as
  \code{sunspot.m2014} for historical and reproducibility reasons.
  For strict reproducibility, hence use that, or \code{\link{sunspots}}
  instead of \code{sunspot.month}.
}
\usage{
sunspot.month
sunspot.m2014
}
\format{
  The univariate time series \code{sunspot.year}, \code{sunspot.m2014}
  and \code{sunspot.month} contain 289, 3177, and currently
  3310
  observations, respectively, where the latter will increase over time.
  The objects are of class \code{"\link{ts}"}.
}
\seealso{
  \code{sunspot.month} is a more up-to-date and hence also longer version of
  \code{\link{sunspots}};
  the latter runs until 1983 and is kept fixed (for reproducibility as example
  dataset).
}
\source{
  \I{WDC-SILSO}, Solar Influences Data Analysis Center (\abbr{SIDC}),
  Royal Observatory of Belgium, Av. Circulaire, 3, B-1180 BRUSSELS
  Currently at \url{https://www.sidc.be/SILSO/datafiles}% was
  % http://www.sidc.be/silso/datafiles, and http://sidc.oma.be/sunspot-data/

  From around 2015, expert astronomers decided to recalibrate historical sunspot
  numbers, see the \sQuote{References}.
  This is \emph{not yet} visible in current \code{sunspot.month} but
  may well change by the next release of \R.
}
\references{
  \bibshow{R:Clette+Lefevre:2016, R:Clette+Lefevre+Chatzistergos:2023}
}
\author{
  R Core Team.
}
\examples{
require(stats); require(graphics)
## Compare the monthly series
plot (sunspot.month,
      main="sunspot.month & sunspots [package 'datasets']", col=2)
lines(sunspots) # -> clear recalibration (to *larger* values)
at. <- seq(1750, 2030, by=10)
atyr <- at.[at. \%\% 50 != 0] #%
Axis(time(sunspot.month), at = atyr, side = 1,
     tck= -1/100, padj = -1.5, cex.axis = 3/4)

## Now look at the difference :
all(tsp(sunspots)     [c(1,3)] ==
    tsp(sunspot.month)[c(1,3)]) ## Start & Periodicity are the same
n1 <- length(sunspots)
table(eq <- sunspots == sunspot.m2014[1:n1]) #>  143  are different !
i <- which(!eq)
rug(time(eq)[i])
s1 <- sunspots[i] ; s2 <- sunspot.m2014[i]
cbind(i = i, time = time(sunspots)[i], sunspots = s1, ss.month = s2,
      perc.diff = round(100*2*abs(s1-s2)/(s1+s2), 1))

## How to recreate the "old" sunspot.month (R <= 3.0.3) =: sunspot.month.0
.sunspot.diff <- cbind(
    i = c(1202L, 1256L, 1258L, 1301L, 1407L, 1429L, 1452L, 1455L,
          1663L, 2151L, 2329L, 2498L, 2594L, 2694L, 2819L),
    res10 = c(1L, 1L, 1L, -1L, -1L, -1L, 1L, -1L,
          1L, 1L, 1L, 1L, 1L, 20L, 1L))
ssm0 <- sunspot.m2014[1:2988]
with(as.data.frame(.sunspot.diff), ssm0[i] <<- ssm0[i] - res10/10)
sunspot.month.0 <- ts(ssm0, start = 1749, frequency = 12)
stopifnot(length(sunspot.month.0) == 2988)
}
\keyword{datasets}