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Finding lengths of identical sequences in lists

• To: mathgroup at smc.vnet.net
• Subject: [mg20240] Finding lengths of identical sequences in lists
• From: Joel Cannon <jcannon at jcannon.washjeff.edu>
• Date: Fri, 8 Oct 1999 18:30:16 -0400
• Sender: owner-wri-mathgroup at wolfram.com

I am looking for a more elegant solution to the following. I have a
list (a list of positions at consecutive times).  I wish to create a
new list of the length of each sequence of consecutive identical
members (including those of length 1). 

For example, for the list {3,2,2,3,3,3,1} I would create the list
{1,2,3,1} because the first 3 appears once, followed by two 2's,
etc. The lists I was working with contained a list of numbers
(e.g. {{x1,y1},{x2,y2},...} rather than simple numbers. I accomplished
this using a while loop, but I suspect there are better ways to do
this using pattern matching or other approaches.

Thanks much.


------------------------------------------------------------------------------
Joel W. Cannon                   |   (724)223-6146         
Dept. of Physics                 |  
Washington and Jefferson College |      
Washington, PA 15301             |      
                                     
                    

• Follow-Ups:
  • Re: Finding lengths of identical sequences in lists
    • From: Maris Tonso <maris@tpu.ee>