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Re: First nonzero in list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg110846] Re: First nonzero in list
  • From: Fred Simons <f.h.simons at tue.nl>
  • Date: Thu, 8 Jul 2010 06:50:33 -0400 (EDT)

Op 08-07-2010 09:13, S. B. Gray schreef:
> 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
>
>
>    
Length[th] - LengthWhile[Reverse[th], # == 0 &]

Regards,

Fred Simons
Eindhoven University of Technology


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