Maximum/Last element of POSIXct column in data.table?

Question

I have a data.table with one column of POSIXcts.

dt <- data.table(DateTime=seq(from=as.POSIXct("2017-02-01 00:00", tz="Europe/Berlin"), by=3600, length.out = 10), Value=1:10)

I thought I can use max(), but that does not work.

maxDateTime <- max(dt[, "DateTime"])

And also last() from 'data.table' package is not doing it:

maxDateTime <- last(dt[, "DateTime"])

Only tail() is going in the right direction

maxDateTime <- tail(dt[, "DateTime"],1)

but returns a data.table, where I only would like to have a single value.

It is a rather simple problem, but I am stuck with it for a while now, so I hope for the right hint here. Thanks!

Ditch the quotes and then all your attempts will work – David Arenburg Feb 17 '17 at 12:40 — David Arenburg, Feb 17 '17 at 12:40

score 2 · Accepted Answer · answered Feb 17 '17 at 11:28

2

We need to use [[ to extract a single column

max(dt[["DateTime"]])

For multiple columns, the syntax is

dt[, c("DateTime", "Value"), with = FALSE]

Or another option is .

dt[, .(DateTime, Value)]

answered Feb 17 '17 at 11:28

akrun

1

Thank you. The first option is totally doing it! – schluk5 Feb 17 '17 at 11:36
1

or `max(df$DateTime)` – mtoto Feb 17 '17 at 11:37

1 Answers1