How to create a datetime object from separate date fields?

Question

I have a dataset like this:

    Year MM DD HH
158 2010  7  1  5
159 2010  7  1  5
160 2010  7  1  6
161 2010  7  1  6

structure(list(Year = c(2010L, 2010L, 2010L, 2010L), MM = c(7L, 
7L, 7L, 7L), DD = c(1L, 1L, 1L, 1L), HH = c(5L, 5L, 6L, 6L)), .Names = c("Year", 
"MM", "DD", "HH"), row.names = 158:161, class = "data.frame")

How can I create a one datetime object from this data set (new column for this data)?

Answer 1

You can now do this in lubridate using make_date or make_datetime:

From the cran doc:

make_datetime(year = 1970L, month = 1L, day = 1L, hour = 0L, min = 0L,
sec = 0, tz = "UTC")

make_date(year = 1970L, month = 1L, day = 1L)

Answer 2

There are a few options, here's one (where x is your data.frame):

x$datetime <- ISOdatetime(x$Year, x$MM, x$DD, x$HH, 0, 0)

You can pass in the correct time zone if need be, see ?ISOdatetime.