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MathGroup Archive 2007

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Re: Map vs. Table

  • To: mathgroup at smc.vnet.net
  • Subject: [mg75407] Re: Map vs. Table
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Sat, 28 Apr 2007 06:02:14 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <f0sfrs$ncb$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

try it out

data = Table[i, {i, 1, 1000000}];

Timing[Table[{i, #} & /@ data[[i]], {i, Length[data]}]][[1]]

gives 2.074 Seconds
and

Timing[
     MapIndexed[{#2[[1]], #} &, data]
     ][[1]]

gives 1.732 Seconds

Regards
   Jens

zac wrote:
> Dear Group,
> 
> consider a set of data (y values):
> 
> data = Table[i*j, {i, 5}, {j, 10}]
> 
> I want to label each Integer with an x value:
> 
> label := Table[{i, #} & /@ data[[i]], {i, Length[data]}]
> 
> I've understand that list creation is much faster with Map than with
> Table.
> Is there an effective way to convert the Table to Map in the label
> function (either with nested Map or to incorporate the Table function
> into the Map)?
> Would it be really faster for very large datasets than with Table?
> 
> thanks
> 
> Istvan Zachar
> 
> 


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