```
# NOT RUN {
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
# }
```

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