Ordering Permutation
orderx
has the same functionality as order,
except that orderx(..., from=from, to=to)
is the same as order[from:to]
orderx(x, from=1, to=length(x), decreasing=FALSE, na.last = NA)
x |
an atomic vector |
from,to |
|
decreasing |
logical. Should the sort order be increasing or decreasing? |
na.last |
for controlling the treatment of |
The smaller the difference to-from is
compared to the length of x, the
faster is orderx compared to order.
Particularly, orderx(..., from=k, to=k)
is much faster than order(...)[k].
orderx is never really slower than order.
For further details see order.
integer vector of length to-from+1.
Martin Schlather, schlather@math.uni-mannheim.de, http://ms.math.uni-mannheim.de
x <- runif(10^6) k <- 10 system.time(y<-order(x)[1:k]) system.time(z<-orderx(x, from=1, to=k)) ## much faster stopifnot(all(x[y ]== x[z])) ## same result
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