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Re: reliably sort?

• To: mathgroup at smc.vnet.net
• Subject: [mg123670] Re: reliably sort?
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Thu, 15 Dec 2011 04:53:37 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <201112141102.GAA10230@smc.vnet.net>
• Reply-to: drmajorbob at yahoo.com

Union always sorts in "canonical order".

If you want unsorted order:

Tally[Join[max,mins]][[All,1]]

Bobby

On Wed, 14 Dec 2011 05:02:50 -0600, Michael Stern <nycstern at gmail.com>  
wrote:

> I have noticed that if combine two lists of date/data objects using
> Union[], the result is sorted by date.
>
> For example
>
> In[]:= mins={{{2001, 1, 31}, 0.993268}, {{2002, 3, 31}, 1.01395},
> {{2003, 6, 30},
>    1.08647}, {{2005, 11, 30}, 1.14752}, {{2006, 9, 30},
>    1.18938}, {{2007, 2, 28}, 1.19658}, {{2008, 1, 31},
>    1.20432}, {{2011, 1, 31}, 1.37501}};
> In[]:= maxs={{{2000, 10, 31}, 1.01816}, {{2001, 12, 31}, 1.02714},
> {{2004, 2, 29},
>     1.12702}, {{2005, 3, 31}, 1.16986}, {{2010, 10, 31}, 1.39026}};
>
> In[]:= Union[maxs, mins]
>
> Out[]= {{{2000, 10, 31}, 1.01816}, {{2001, 1, 31},
>    0.993268}, {{2001, 12, 31}, 1.02714}, {{2002, 3, 31},
>    1.01395}, {{2003, 6, 30}, 1.08647}, {{2004, 2, 29},
>    1.12702}, {{2005, 3, 31}, 1.16986}, {{2005, 11, 30},
>    1.14752}, {{2006, 9, 30}, 1.18938}, {{2007, 2, 28},
>    1.19658}, {{2008, 1, 31}, 1.20432}, {{2010, 10, 31},
>    1.39026}, {{2011, 1, 31}, 1.37501}}
>
> Is this reliable behavior? Is there any case in which Union would /not/
> return results that have been properly sorted by date?
>
> Thank you,
>
> -Michael Stern


-- 
DrMajorBob at yahoo.com

• Follow-Ups:
  • Re: reliably sort?
    • From: Andy Ross <andyr@wolfram.com>

• References:
  • Does Union[] reliably sort?
    • From: Michael Stern <nycstern@gmail.com>