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 >