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MathGroup Archive 2001

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Re: Searching for embedded zeros in list

  • To: mathgroup at
  • Subject: [mg32147] Re: Searching for embedded zeros in list
  • From: Erich Neuwirth <erich.neuwirth at>
  • Date: Sat, 29 Dec 2001 18:00:25 -0500 (EST)
  • References: <a0jlsc$31m$>
  • Sender: owner-wri-mathgroup at

how about:
cut off leading and trailing zeros,
and them multiply the remains.
if the product is 0, there are embedded zeros,
otherwise not.

"Coleman, Mark" wrote:
> Greetings,
> Can anyone suggest an efficient/elegant way of checking a list for
> 'embedded' zeros. By embedded I mean the occurence of one or more zeros
> between two non-zero elements (note: zeros at the ends of the list are
> not relevant). For instance, the following lists all contain embedded
> zeros:
>    a={0.98,0.87,0.0,0.5,0.25}
>    b={0.9,0.0,0.0,0.0,0.0,0.0,0.05}
>    c={0.75,0.42,0.10,0.0,0.03}
> while this list does not d={0.0,0.90,0.75,0.42,0.25,0.0}
> By way of background, I am working on a problem involving estimating
> generators for Markov transition matrices. One condition that ensures
> that a generator *does not* exist is the presence of inaccessible states
> in any row of the matrix. Thus one need only find a single occurance of
> an inaccessible state to show that a generator does not exist. Hence the
> code need only locate one such state, not all of them.
> The Mathematica code I've written for this problem does work, but it is hardly
> "elegant".
> Any help would be much appreciated!
> Best regards,
> -Mark

Erich Neuwirth, Computer Supported Didactics Working Group
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