dear kind helper,
i would like to know how to find the annual maximun for a table that
basicly looks like this:
date time measurement1 measurement2 measurement3
mm/dd/yyyy hh:mm:ss m1 m2 m3
there are about 9000 measurements for each year, which makes it quite
large...
i already tried to subset all rows for a year, to find the maximum
within these choosen rows,
y <- grep(yyyy,table[,1],value=TRUE)
df <-table[with(table, date == y), ]
df[with(df, max(measurement1)), ]
which got result some years, but didn't show all rows within these
years, and for other years it didn't work at all,
V1 V2 V3 V4 V5
NA <NA> <NA> NA NA NA
or/and gave warnings like:
Warning messages:
1: longer object length
is not a multiple of shorter object length in: is.na(e1) | is.na(e2)
2: longer object length
is not a multiple of shorter object length in:
`==.default`(date, y)
i also tried:
result <- matrix(nrow=0,ncol=2)
for (y in yyyy:yyyy) {
Y <- grep(y, table[,1],value=TRUE)
Max <- max (subset(table, date %in% Y, c(date, measurement1))[,2])
result2 <- (c(y,Max))
result <- rbind(result2,result)
}
print(result)
that kind of worked, but only gave me the year in the result, but i need
the full date, for the statistical analysis.
i hope you can help me with this,
thank you in advance,
d.salecker
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