[R] about the function order()
charpent at bacbuc.dyndns.org
Tue Nov 27 15:28:41 CET 2001
According to Thomas Lumley :
>In a sense it's doing the opposite of what you thought.
>The definition of order() is basically that
>is in increasing order. This works with your example, where the correct
>order is the fourth, second, first, then third element.
>You may have been looking for rank(), which returns the rank of the
/>R> a <- c(4.1, 3.2, 6.1, 3.1) /
/>R> order(a) /
> 4 2 1 3
/>R> rank(a) /
> 3 2 4 1
>so rank() tells you what order the numbers are in, order() tells you how
>to get them in ascending order.
Hmmm ... meaning that order behaves like the (gradeup) APL function,
right ? (Yes, I'm *that* old ...).
That should imply that, barring possible ties, rank(x) ==
order(order(x)). Right ?
So : why distinc implementations ? Are there efficiency considerations
I'm missing ?
Or am I completely mistaken ?
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