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Re: First nonzero in list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg110853] Re: First nonzero in list
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 8 Jul 2010 07:41:23 -0400 (EDT)

th = {227, 342, 527, 0, 670, 730, 703, 0, 0, 649, 687, 614, 570, 501, 
   462, 402, 325, 254, 189, 99, 81, 36, 9, 8, 3, 0, 0, 0, 0, 0, 0, 0, 
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};

th /. {a___, 0 ..} :> {a} // Length

25

th /. {a___, 0 ..} :> Length[{a}]

25


Bob Hanlon

---- "S. B. Gray" <stevebg at ROADRUNNER.COM> wrote: 

=============
I have lists such as

th = {227, 342, 527, 0, 670, 730, 703, 0, 0, 649, 687, 614, 570, 501,
   462, 402, 325, 254, 189, 99, 81, 36, 9, 8, 3, 0, 0, 0, 0, 0, 0, 0,
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}

and I want to find the position of the last nonzero element (e.g. 3 at 
position 25). Trivial, but some poking around did not reveal a neat way.

Anyone? Thank you.

Steve Gray




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