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MathGroup Archive 2007

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Re: Sorting by date

  • To: mathgroup at smc.vnet.net
  • Subject: [mg72655] Re: [mg72637] Sorting by date
  • From: Carl Woll <carlw at wolfram.com>
  • Date: Sun, 14 Jan 2007 04:06:35 -0500 (EST)
  • References: <200701130917.EAA24117@smc.vnet.net>

Clifford Martin wrote:

>Hi All,
>
>I have a list of lists that looks like so:
>
>
>{{3, 137.5, 13978, {2005, 2, 8}}, {3, 138.5, 12519, {2005, 1, 4}}, {3, 171.9, 15835, {2005, 4, 12}}, {3, 142.8, 17137, {2005, 11, 19}}, 
>  {3, 161.1, 18881, {2006, 1, 18}}, {3, 108.7, 20055, {2006, 2, 28}}, {3, 157, 21498, {2006, 9, 14}}, {3, 118.1, 10891, {2004, 11, 12}}}
>
>The last element per vector is a date. I'd like to sort the list so that the vectors are arranged in ascending order of date, i.e. the vector containing {2004,11,12}  should be first and and the vector containing {2006,9,14}  should be last. Any help would be appreciated.
>
>Thanks
>
>Cliff
>  
>
In my opinion, the best method for these kinds of problems is to use 
Ordering. For example:

lst={{3,137.5,13978,{2005,2,8}},{3,138.5,12519,{2005,1,4}},{3,171.9,15835,{2005,4,12}},
{3,142.8,17137,{2005,11,19}},{3,161.1,18881,{2006,1,18}},{3,108.7,20055,{2006,2,28}},
{3,157,21498,{2006,9,14}},{3,118.1,10891,{2004,11,12}}};

lst[[  Ordering[ lst[[All,-1]] ]  ]]
{{3,118.1,10891,{2004,11,12}}, {3,138.5,12519,{2005,1,4}}, 
{3,137.5,13978,{2005,2,8}},
{3,171.9,15835,{2005,4,12}},{3,142.8,17137,{2005,11,19}},{3,161.1,18881,{2006,1,18}},
{3,108.7,20055,{2006,2,28}},{3,157,21498,{2006,9,14}}}

Carl Woll
Wolfram Research


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