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MathGroup Archive 2007

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Re: Map vs. Table

  • To: mathgroup at smc.vnet.net
  • Subject: [mg75394] Re: Map vs. Table
  • From: dimitris <dimmechan at yahoo.com>
  • Date: Sat, 28 Apr 2007 05:55:22 -0400 (EDT)
  • References: <f0sfrs$ncb$1@smc.vnet.net>

Hi.

In[54]:=
data = Table[i*j, {i, 5}, {j, 10}]

Out[54]=
{{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, {2, 4, 6, 8, 10, 12, 14, 16, 18,
20}, {3, 6, 9, 12, 15, 18, 21, 24, 27, 30},
  {4, 8, 12, 16, 20, 24, 28, 32, 36, 40}, {5, 10, 15, 20, 25, 30, 35,
40, 45, 50}}

In[68]:=
(Partition[Insert[data[[#1]], #1, Partition[Range[10], 1]], 2] & ) /@
Range[5]

Out[68]=
{{{1, 1}, {1, 2}, {1, 3}, {1, 4}, {1, 5}, {1, 6}, {1, 7}, {1, 8}, {1,
9}, {1, 10}},
  {{2, 2}, {2, 4}, {2, 6}, {2, 8}, {2, 10}, {2, 12}, {2, 14}, {2, 16},
{2, 18}, {2, 20}},
  {{3, 3}, {3, 6}, {3, 9}, {3, 12}, {3, 15}, {3, 18}, {3, 21}, {3,
24}, {3, 27}, {3, 30}},
  {{4, 4}, {4, 8}, {4, 12}, {4, 16}, {4, 20}, {4, 24}, {4, 28}, {4,
32}, {4, 36}, {4, 40}},
  {{5, 5}, {5, 10}, {5, 15}, {5, 20}, {5, 25}, {5, 30}, {5, 35}, {5,
40}, {5, 45}, {5, 50}}}

Dimitris

=CF/=C7 zac =DD=E3=F1=E1=F8=E5:
> 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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