Pattern problem: How to count from a long list of numbers all occurrences of 2 numbers next to each others?
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- Subject: [mg87393] Pattern problem: How to count from a long list of numbers all occurrences of 2 numbers next to each others?
- From: "Nasser Abbasi" <nma at 12000.org>
- Date: Wed, 9 Apr 2008 05:56:39 -0400 (EDT)
- Reply-to: "Nasser Abbasi" <nma at 12000.org>
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 :)
- Follow-Ups:
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- From: Carl Woll <carlw@wolfram.com>
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- From: "W Craig Carter" <ccarter@mit.edu>
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- From: Andrzej Kozlowski <akoz@mimuw.edu.pl>
- Re: Pattern problem: How to count from a long list of numbers