Re: Pattern problem: How to count from a long list of numbers all occurrences of 2 numbers next to each others?
- To: mathgroup at smc.vnet.net
- Subject: [mg87412] Re: [mg87393] Pattern problem: How to count from a long list of numbers all occurrences of 2 numbers next to each others?
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Thu, 10 Apr 2008 02:10:53 -0400 (EDT)
- References: <200804090956.FAA25006@smc.vnet.net>
I think this will work:
ls = {1, 3, 3, 3, 2, 3, 3, 1, 3, 3}
Total[ReplaceList[ls, {___, 3, 3, ___} -> 1]]
4
Total[ReplaceList[ls, {___, 1, 3, ___} -> 1]]
2
etc.
Andrzej Kozlowski
On 9 Apr 2008, at 18:56, 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 :)
>
>
- References:
- Pattern problem: How to count from a long list of numbers all occurrences of 2 numbers next to each others?
- From: "Nasser Abbasi" <nma@12000.org>
- Pattern problem: How to count from a long list of numbers all occurrences of 2 numbers next to each others?