Re: Request for help: working with multi-level lists

*To*: mathgroup at smc.vnet.net*Subject*: [mg13681] Re: Request for help: working with multi-level lists*From*: "David Keith" <dkeith at hevanet.com>*Date*: Sat, 15 Aug 1998 04:39:13 -0400*Organization*: Hevanet Communications*References*: <6qp3mc$al3@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Try this: <<Statistics`DescriptiveStatistics` Mean[ Transpose[Select[list,#1[[1]]==1&]][[2]] ] Select uses a pure function to choose those elements for which element[[1]] ==1, Transpose transposes the list so that it is now is a list of three lists, the 2nd of which is a list of the 2nd elements, then [[2]] chooses just that list and Mean computes the average. "<<Statistics`DescriptiveStatistics`" loads Mean. Dave KCConnolly wrote in message <6qp3mc$al3 at smc.vnet.net>... >I have a list of 10 elements, each of which is a list of three elements >(let's say in each case an integer, a real number, and a string). I am >looking for the most elegant way to select those first-level elements >(i.e., the lists) whose integer element is equal to a particular value >(let's say "1"), and then to obtain the mean of the real number >elements of the lists selected. This seems as if it should be simple, >but everything I try leads to Part specification errors. Any help >would be greatly appreciated. >