       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[], (2*Pi*#1[])^2*U/#1[]} & ) /@ thelist ==
(thelist /. {x_, y_} :> {x, (2*Pi*x)^2*U/y}) ==
Cases[thelist, {x_, y_} :> {x, (2*Pi*x)^2*U/y}] ==

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?
>

```

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