On 2007-08-03, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
> A naive approach to rank ordering (handling ties as well) of nested
> lists may be accomplished via:
>
> def rankLists(nestedList):
> def rankList(singleList):
> sortedList = list(singleList)
> sortedList.sort()
> return map(sortedList.index, singleList)
> return map(rankList, nestedList)
>
> >>> unranked = [ [ 1, 2, 3, 4, 5 ], [ 3, 1, 5, 2, 4 ], [ -1.1, 2.2,
> 0, -1.1, 13 ] ]
> >>> print rankLists(unranked)
>
> [[0, 1, 2, 3, 4], [2, 0, 4, 1, 3], [0, 3, 2, 0, 4]]
>
> This works nicely when the dimensions of the nested list are
> small. It is slow when they are big. Can someone suggest a
> clever way to speed it up?
Use binary search instead of linear.
import bisect
import functools
def rankLists(nestedList):
def rankList(singleList):
sortedList = list(sorted(singleList))
return map(functools.partial(bisect.bisect_left, sortedList), singleList)
return map(rankList, nestedList)
--
Neil Cerutti
Facts are stupid things. --Ronald Reagan
--
http://mail.python.org/mailman/listinfo/python-list
