Re: sequential elements of list
- To: mathgroup at smc.vnet.net
- Subject: [mg119308] Re: sequential elements of list
- From: Bill Rowe <readnews at sbcglobal.net>
- Date: Mon, 30 May 2011 06:33:52 -0400 (EDT)
On 5/29/11 at 7:38 AM, Paul.McHale at excelitas.com (McHale, Paul)
wrote:
>Does anyone know of a way to use a pure function to access current
>and next element of list with uses like Select[]? I know I might be
>dazed and confused, but I thought there was a way. I.e.
>mList={1,2,3,4,5,7,6,8};
>Select[mList, (#? > #??)&]
>Where #? Is element N and #?? Is element N+1. I would expect the
>previous code (assuming N?, N?? were valid) to return 7.
It is not clear to me what you want for an output. If you want a
list of all {mList[[n]],mList[[n+1]]} pairs, this is easily
accomplished with
Partition[mList,2,1]
If you want a specific pair, say {4,5} from the list above, then
there are a number of ways to accomplish this such as
Cases[Partition[mList,2,1],{4,_}]
or
mList[[{#,#+1}]]&[Position[mList,4][[1,1]]]