Using Part

• To: mathgroup at smc.vnet.net
• Subject: [mg77057] Using Part
• From: Clifford Martin <camartin at snet.net>
• Date: Sat, 2 Jun 2007 04:15:18 -0400 (EDT)

```  Group,

I need some educational help. Below is a list of lists I'm trying to manipulate. Notice that the date is in the 6th place in each list.  What I want to do is 1) identify the lists with identical dates and 2) once I've done that add the third element of each list with identical dates together and 3) eliminate the two original lists.

{{{16871,I7,614,48876,850,{2006,12,2}},{16871,I7,538.3,49803,850,{2007,1,8}},
{16871,I7,474.8,50655,850,{2007,2,1}},{16871,I7,428.1,51430,850,{2007,2,20}},
{16871,I7,74.9,51430,850,{2007,2,20}},{16871,I7,535,52348,850,{2007,3,20}},
{16871,I7,395.9,53383,850,{2007,5,9}}}

So what I would end up with would be:

{{{16871,I7,614,48876,850,{2006,12,2}},{16871,I7,538.3,49803,850,{2007,1,8}},
{16871,I7,474.8,50655,850,{2007,2,1}},{16871,I7,503,51430,850,{2007,2,20}},
{16871,I7,535,52348,850,{2007,3,20}},{16871,I7,395.9,53383,850,{2007,5,9}}}

There is something about using Part that I'm not understanding. In the list below if I say:
Part[list,4,6]==Part[list,5,6] I get
True

but if I try to find it with an anonymous function like
Select[list,Part[#1,6]==Part[#2,6] this doesn't find it. Clearly I'm not understanding how to use these functions with Part. I've tried many variations of this and it just shows I'm not understanding something fundamental.