sunspot.year | R Documentation |

## Yearly Sunspot Data, 1700–1988

### Description

Yearly numbers of sunspots from 1700 to 1988 (rounded to one digit).

Note that monthly numbers are available as
`sunspot.month`

, though starting slightly later.

### Usage

sunspot.year

### Format

The univariate time series `sunspot.year`

contains 289
observations, and is of class `"ts"`

.

### Source

H. Tong (1996)
*Non-Linear Time Series*. Clarendon Press, Oxford, p. 471.

### See Also

For *monthly* sunspot numbers, see `sunspot.month`

and `sunspots`

.

Regularly updated yearly sunspot numbers are available from
WDC-SILSO, Royal Observatory of Belgium, at
http://www.sidc.be/silso/datafiles

### Examples

utils::str(sm <- sunspots)# the monthly version we keep unchanged
utils::str(sy <- sunspot.year)
## The common time interval
(t1 <- c(max(start(sm), start(sy)), 1)) # Jan 1749
(t2 <- c(min( end(sm)[1],end(sy)[1]), 12)) # Dec 1983
s.m <- window(sm, start=t1, end=t2)
s.y <- window(sy, start=t1, end=t2[1]) # {irrelevant warning}
stopifnot(length(s.y) * 12 == length(s.m),
## The yearly series *is* close to the averages of the monthly one:
all.equal(s.y, aggregate(s.m, FUN = mean), tol = 0.0020))
## NOTE: Strangely, correctly weighting the number of days per month
## (using 28.25 for February) is *not* closer than the simple mean:
ndays <- c(31, 28.25, rep(c(31,30, 31,30, 31), 2))
all.equal(s.y, aggregate(s.m, FUN = mean)) # 0.0013
all.equal(s.y, aggregate(s.m, FUN = weighted.mean, w = ndays)) # 0.0017