first {data.table} | R Documentation |
Returns the first item of a vector or list, or the first row of a data.frame or data.table.
first(x, ...)
x |
A vector, list, data.frame or data.table. Otherwise the S3 method
of |
... |
Not applicable for |
If no other arguments are supplied it depends on the type of x. The first item
of a vector or list. The first row of a data.frame
or data.table
.
Otherwise, whatever xts::first
returns (if package xts has been loaded,
otherwise a helpful error).
If any argument is supplied in addition to x
(such as n
or
keep
in xts::first
), regardless of x
's type, then
xts::first
is called if xts has been loaded, otherwise a helpful error.
first(1:5) # [1] 1 x = data.table(x=1:5, y=6:10) first(x) # same as x[1]