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Re: Pattern problem: How to count from a long list of

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87443] Re: [mg87393] Pattern problem: How to count from a long list of
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 10 Apr 2008 02:17:01 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

x = {1, 3, 3, 3, 2, 3, 3, 1, 3, 3};

Count[Partition[x, 2, 1], {3, 3}]

4

Count[Partition[x, 2, 1], {1, 3}]

2


Bob Hanlon

---- Nasser Abbasi <nma at 12000.org> wrote: 
> Hello;
> 
> I think using Pattern is my weakest point in Mathematica.
> 
> I have this list, say this: (it is all a list of integers, no real numbers).
> 
> x = {1, 3, 3, 3, 2, 3, 3, 1, 3, 3}
> 
> And I want to count how many say a 3 followed immediately by 3. So in the 
> above list, there will be 4 such occurrences. And if I want to count how 
> many 1 followed by a 3, there will be 2 such cases, etc...
> 
> I tried Count[] but I do not know how to set the pattern for "3 followed by 
> a comma followed by 3" or just "3 followed immediately by 3".
> 
> I tried few things, such as the following
> 
> In[68]:= Count[x, {3, 3}_]
> Out[68]= 0
> 
> Also tried Cases, but again, I am not to good with Patterns, so not sure how 
> to set this up at this moment.
> 
> Any ideas will be appreciated.
> 
> Nasser
> I really need to sit down and study Patterns in Mathematica really well one 
> day :) 
> 
> 



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