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Add terms surrounded by zero together in matrix

• To: mathgroup at smc.vnet.net
• Subject: [mg59123] Add terms surrounded by zero together in matrix
• From: "mchangun at gmail.com" <mchangun at gmail.com>
• Date: Fri, 29 Jul 2005 00:42:08 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

Hi All,

I think this is a rather tough problem to solve.  I'm stumped and would
really appreciated it if someone can come up with a solution.

What i want to do is this.  Suppose i have the following matrix:

0       0       0       1       0
0       0       1       2       0
0       0       0       2       1
1       3       0       0       0
0       0       0       0       0
0       0       0       0       0
0       0       1       1       0
5       0       3       0       0
0       0       0       0       0
0       0       0       3       1

I'd like to go through it and sum the elements which are surrounded by
zeros.  So for the above case, an output:

[7 4 5 5 4]

is required.  The order in which the groups surrounded by zero is
summed does not matter.

The elements are always integers greater than 0. 

Thanks for any help!

• Follow-Ups:
  • Re: Add terms surrounded by zero together in matrix
    • From: Andrzej Kozlowski <akoz@mimuw.edu.pl>
  • Re: Add terms surrounded by zero together in matrix
    • From: "Fred Simons" <f.h.simons@tue.nl>