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MathGroup Archive 2007

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Partition a list into sublists of unequal size

  • To: mathgroup at smc.vnet.net
  • Subject: [mg83919] Partition a list into sublists of unequal size
  • From: antf <anthonyfox at gmail.com>
  • Date: Tue, 4 Dec 2007 04:29:39 -0500 (EST)

Hello,

I have a list that looks like the following:

list={1,0,0,1,0,0,1,1,0,1,0,0,0,0,1,0}

I then find the positions of the 1s in the list:

positions = Flatten@Position[list,1]

{1,4,7,8,10,15}

I then want to partition a third list into sublists so that the first
sublist is from index 1;;1, the second sublist is from index 2;;4, the
third sublist is from index 5;;7, the fourth sublist is just element
8, etc.

Currently, I use Partition on the positions sublist with overlap as
in:

Partition[Join[{1},positions],2,1]

{{1,1},{1,4},{4,7},{7,8},{8,10},{10,15}}

I then use this list to partition the target list by Mapping Take to
each element of this list and adjusting the first index appropriately.

I am sure there must be a simpler way to do this.  Can anyone tell me
how to do this operation?

Thanks,
Anthony


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