First/last item of an object
Returns the first/last item of a vector or list, or the first/last row of a data.frame
or data.table. The main difference to head/tail is that the default for n is 1
rather than 6.
first(x, n=1L, ...) last(x, n=1L, ...)
x |
A vector, list, data.frame or data.table. Otherwise the S3 method
of |
n |
A numeric vector length 1. How many items to select. |
... |
Not applicable for |
If no other arguments are supplied it depends on the type of x. The first/last item
of a vector or list. The first/last row of a data.frame or data.table.
For other types, or if any argument is supplied in addition to x (such as n, or
keep in xts) regardless of x's type, then xts::first/
xts::last is called if xts has been loaded, otherwise utils::head/utils::tail.
first(1:5) # [1] 1 x = data.table(x=1:5, y=6:10) first(x) # same as head(x, 1) last(1:5) # [1] 5 x = data.table(x=1:5, y=6:10) last(x) # same as tail(x, 1)
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