I presume you want this separately for each of V3, V4 and V5,
and illustrated V4?
Let's first create a new column for the year. If the table is 'tab':
tab$year <- substring(tab$V1, 7)
Then by() almost does the job, but we need to reformat the result.
myfun <- function(tab, col) {
i <- which.max(tab[[col]])[1]
tab[i, c("V1", col)]
}
do.call("rbind", by(tab, tab$year, myfun, col="V4"))
which gives
V1 V4
1975 01/01/1975 3.691
1976 02/24/1976 2.623
1977 10/18/1977 2.559
1978 11/05/1978 2.605
1979 06/29/1979 3.325
on your example.
On Tue, 13 Nov 2007, "Dörte Salecker" wrote:
dear r-helpers
i've got a table that in extracts looks like this:
V1 V2 V3 V4 V5
1 01/01/1975 00:00:00 125.837 3.691 296.618
2 01/01/1975 01:00:00 124.799 3.679 281.307
3 01/01/1975 02:00:00 111.607 3.536 281.307
4 02/24/1976 11:00:00 21.602 2.555 93.893
5 02/24/1976 12:00:00 27.804 2.623 93.893
6 02/24/1976 13:00:00 26.105 2.604 114.716
7 10/18/1977 00:00:00 18.850 2.525 330.203
8 10/18/1977 01:00:00 21.561 2.555 320.465
9 10/18/1977 02:00:00 21.941 2.559 314.505
10 11/05/1978 01:00:00 24.981 2.592 310.464
11 11/05/1978 02:00:00 19.066 2.528 310.464
12 11/05/1978 03:00:00 26.198 2.605 305.749
13 06/29/1979 19:00:00 78.829 3.179 306.199
14 06/29/1979 20:00:00 92.221 3.325 306.199
15 06/29/1979 21:00:00 72.364 3.108 303.049
i need to find the annual maximun for each year in V3, V4 and V5 So that
the result would be a table like this:
V1 V4
1 01/01/1975 3.691
2 02/24/1976 2.623
3 10/18/1977 2.559
.
.
.and so on.
i hope you can help me with this,
thank you in advance,
doerte
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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