Re: Selecting Sub-lists After Split
- To: mathgroup at smc.vnet.net
- Subject: [mg77455] Re: Selecting Sub-lists After Split
- From: DrMajorBob <drmajorbob at bigfoot.com>
- Date: Sat, 9 Jun 2007 05:32:21 -0400 (EDT)
walk == Rest@NestList[# + Random[] - 1/2 &, 0, 1000];
signedRuns == Split[walk, #1 #2 > 0 &];
Length /@ signedRuns
negativeRuns == Select[signedRuns, First[#] < 0 &];
Length /@ negativeRuns
{12, 11, 2, 22, 1, 207, 2, 3, 78, 1, 202, 38, 66, 355}
{12, 2, 1, 2, 78, 202, 66}
I didn't let negativeRuns display, but I think that's what you wanted.
Bobby
On Fri, 08 Jun 2007 04:34:49 -0500, Gregory Lypny
<gregory.lypny at videotron.ca> wrote:
> Hello everyone,
>
> Suppose I have a list of real number called myList. I split it into
> sub-lists of positive and negative numbers called myNewList by doing
> this (there may be a more elegant way):
>
> myNewList == Split[myList, #1 #2 > 0 &]
>
> Now, how can I select all of the sub-lists of negative numbers from
> myNewList?
>
> Any tips would be most appreciated.
>
> Regards,
>
> Gregory
>
>
--
DrMajorBob at bigfoot.com