Re: Converting a mapping into a well-defined function

*To*: mathgroup at smc.vnet.net*Subject*: [mg56544] Re: Converting a mapping into a well-defined function*From*: "Carl K. Woll" <carl at woll2woll.com>*Date*: Thu, 28 Apr 2005 02:40:46 -0400 (EDT)*References*: <79344CBB6297454F86DD3106ADCC76CC82F394@mail3.nwfwmd.state.fl.us>*Sender*: owner-wri-mathgroup at wolfram.com

Gilmar wrote: > Dear Carl: > Your map sorts the set A. > For example, if A={{47, 53}, {31, 61}, {43, 53}, {43, 47}, {37, 61}}; > then using your f[x_] module, we get f[A]= {{31, 61}, {37, 61}, {43, > 53}, {47, 53}}, when it should be: > {{47, 53}, {31, 61}, {43, 53}, {37, 61}}; i.e. an unsorted set. > Nevertheless I don't mind having your version since it can still come > handy. It's a simple matter to modify the code to return an unsorted version: f[x_]:=Module[{tmp}, tmp = Transpose[{x[[All,1]],Range[Length[x]],x[[All,2]]}]; tmp = Split[Sort[tmp], #1[[1]]===#2[[1]]&][[All,1]]; tmp[[Ordering[tmp[[All,2]]]]][[All,{1,3}]] ] Testing: A={{47, 53}, {31, 61}, {43, 53}, {43, 47}, {37, 61}}; f[A] {{47, 53}, {31, 61}, {43, 53}, {37, 61}} [snip] Carl Woll