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MathGroup Archive 2004

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Re: Joining 2D arrays

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49152] Re: Joining 2D arrays
  • From: Jonathan Greenberg <greenberg at ucdavis.edu>
  • Date: Mon, 5 Jul 2004 04:54:37 -0400 (EDT)
  • References: <cc2uns$5iv$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Thanks to all who answered!  Below are the responses I got:

***

Join[A,B]

***

That essentially depends on how you get at your tables. If you have them
available altogether in a single List, then just Apply Join (see Help >
Join, Apply). It will then take you a second or two (or less), but avoid
building up your database incrementally: that will take you the day.

See also (Help > Reep, Sow).

***

Hello !
 
Several possibilities...
 
Here two of them  (in your example, modified to see the ordering problem)
 
A={{1,2},{8,9},{5,6}}

B={{6,7},{3,4},{10,11},{12,13}}

Join[A,B]

{{1,2},{8,9},{5,6},{6,7},{3,4},{10,11},{12,13}}

Flatten[{A,B},1]

{{1,2},{8,9},{5,6},{6,7},{3,4},{10,11},{12,13}}

You could also use Union[A,B], but in this case, the ordrer will be
re-arranged :
Union[A,B]

{{1,2},{3,4},{5,6},{6,7},{8,9},{10,11},{12,13}}

***

Following should work to join two lists:
Join[A,B] or
Append[A,B]

***

--j


On 7/1/04 11:18 PM, in article cc2uns$5iv$1 at smc.vnet.net, "Jonathan
Greenberg" <greenberg at ucdavis.edu> wrote:

> This is a total newbie question, but if I have two table of a fixed number
> of columns and an arbitrary number of rows, whats the easiest/most efficient
> way to join them together (basically, how do I add entries to a "database"
> in Mathematica) -- that database will eventually be perhaps > 1,000,000
> entries long...
> 
> A={{1,2},{3,4},{5,6}}
> B={{6,7},{8,9},{10,11},{12,13}}
> 
> I want:
> 
> {{1,2},{3,4},{5,6},{6,7},{8,9},{10,11},{12,13}}
> 
> --j
> 


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