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Re: Mapping tag-value lists to a third

  • To: mathgroup at smc.vnet.net
  • Subject: [mg132444] Re: Mapping tag-value lists to a third
  • From: Francisco Gutierrez <fgutiers2002 at yahoo.com>
  • Date: Tue, 18 Mar 2014 01:27:44 -0400 (EDT)
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  • Reply-to: Francisco Gutierrez <fgutiers2002 at yahoo.com>

What about Extract[val, Position[tag, 1]]?
Francisco


On Monday, March 17, 2014 1:33 AM, "carlos.felippa%colorado.edu at gtempaccount.com" <carlos.felippa%colorado.edu at gtempaccount.com> wrote:
Hi,

I have 2 lists of equal length such as

tag={0, 1, 0, 0, 0, 1, 0, 1};  val={f1,f2,f3,f4,f5,f6,f7,f8}

and want to produce a third:

tagval={f2,f6,f8}

with length Count[tag,1] containing the entries of val marked by 1-tags. Should be
something efficient, since the source lists may be large (10^6 to 10^7).  Thanks.



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