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

  • To: mathgroup at smc.vnet.net
  • Subject: [mg87439] Re: Pattern problem: How to count from a long list of numbers all
  • From: dh <dh at metrohm.ch>
  • Date: Thu, 10 Apr 2008 02:16:09 -0400 (EDT)
  • References: <fti404$ok1$1@smc.vnet.net>


Hi Nasser,

ReplaceList does not quit what you want, but you can fix it up:

Length@ReplaceList[x,{___,3,3,___}->0]

hope this helps, Daniel



Nasser Abbasi 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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