Request for help: working with multi-level lists

*To*: mathgroup at smc.vnet.net*Subject*: [mg13665] Request for help: working with multi-level lists*From*: kcconnolly at aol.com (KCConnolly)*Date*: 11 Aug 1998 02:24:02 GMT*Organization*: AOL http://www.aol.com*Sender*: owner-wri-mathgroup at wolfram.com

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.

**Follow-Ups**:**Re: Request for help: working with multi-level lists***From:*"Carl K.Woll" <carlw@fermi.phys.washington.edu>