Re: Manipulating a list of pairs

*To*: mathgroup at smc.vnet.net*Subject*: [mg19733] Re: [mg19689] Manipulating a list of pairs*From*: BobHanlon at aol.com*Date*: Mon, 13 Sep 1999 02:41:01 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Hans, lumpi[{f_, amp_}] := {f, Power[2 Pi f, 2] U / amp}; thelist = Table[ToExpression[ "{x" <> ToString[k] <> ", y" <> ToString[k] <> "}"], {k, 5}]; The following expressions are equivalent lumpi /@ thelist == ({#1[[1]], (2*Pi*#1[[1]])^2*U/#1[[2]]} & ) /@ thelist == (thelist /. {x_, y_} :> {x, (2*Pi*x)^2*U/y}) == Cases[thelist, {x_, y_} :> {x, (2*Pi*x)^2*U/y}] == MapThread[{#1, (2*Pi*#1)^2*U/#2} & , Transpose[thelist]] True However, I don't think they are any easier nor are they any easier to understand. Bob Hanlon In a message dated 9/11/1999 9:42:15 PM, hans.steffani at e-technik.tu-chemnitz.de writes: >I have a list of pairs and manipulate it with things like > >lumpi[{f_, amp_}]:={f, Power[2 Pi f,2] U / amp} >Map[ lumpi, thelist] > >is there an easier way without introducing "lumpi" to do this? >