Re: How to find the index of a maximal element in a list?

*To*: mathgroup at smc.vnet.net*Subject*: [mg72955] Re: How to find the index of a maximal element in a list?*From*: "Mark Westwood" <markc.westwood at gmail.com>*Date*: Fri, 26 Jan 2007 07:06:35 -0500 (EST)*References*: <epa2rr$iue$1@smc.vnet.net>

Hi Victor No, off the top of my head I couldn't think of a neater way of doing this, but I'm not sure that I am or should be bothered. I created a randomly ordered list of the first 500000 integers, and used your approach to find the position of the maximum element. Fast enough for my purposes In[10]:=list3=RandomPermutation[500000]; In[11]:=Timing[Position[list3,Max[list3]]] Out[11]={0.094 Second,{{180740}}} Why do you think that this approach traverses the list twice ? I could write it in Fortran with a single traversal of the list, something like this (WARNING: untested code follows): integer, dimension(500000) :: alist maxelement = alist(1) maxelement_location = 1 do i = 2, size(alist) if (alist(i) > maxelement) then maxelement = alist(i) ! not required if you're only looking for a position maxelement_location = i end if end do Of course, if I was writing it in Fortran I'd use the maxloc intrinsic ... Regards Mark Westwood On 25 Jan, 11:04, Valter Sorana <vsor... at yahoo.com> wrote: > I may have a mental block, but I cannot find anything better than > > Position[listName,Max[listName]] > > that traverses the list twice - once to find the maximum and once to find where it is. > > Isn't there a way to get both the index and the max value in one go? > > (of course one could write a loop that does this, but I want to avoid loops) > > Thanks, > > Valter.