       Q:Nicer than: Function[x,MapAt[Im,x,2]]/@data

• To: mathgroup at smc.vnet.net
• Subject: [mg5466] [mg5389] Q:Nicer than: Function[x,MapAt[Im,x,2]]/@data
• From: Allan Hayes <hay at haystack>
• Date: Sat, 7 Dec 1996 00:26:47 -0500
• Sender: owner-wri-mathgroup at wolfram.com

```rommel at bc.edu
[mg5389] Q:Nicer than:  Function[x,MapAt[Im,x,2]]/@data
writes
>>>>>>
I want to ListPlot the imaginary part of data:

data={{x0,z0},{x1,z1},{x2,z2}}

The x? are real, the z? complex.

My simple but ugly solution was

Transpose[{Transpose[data][],Im[Transpose[data][]]}]

after reading a little I came to the shorter

Function[x,MapAt[Im,x,2]]/@data

Is there a nicer way to do it?
<<<<<<

Some Experiments:

lst = Table[{Random[],Random[]+I Random[]},{2000}];

{1.25 Second, Null}

MapAt[Im,#,2]&/@lst;//Timing                     (*faster function*)
{0.7 Second, Null}

Apply[{#,Im[#2]}&,lst,1];//Timing                (*use Apply*)
{0.466667 Second, Null}

lst/.Complex[x_,y_]:>y;//Timing			 (*pattern matching*)
{0.483333 Second, Null}

lst/.{a_,Complex[x_,y_]}:>{a,y};//Timing         (*help matching*)
{0.383333 Second, Null}

{0.3 Second, Null}