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: [mg87577] Re: Pattern problem: How to count from a long list of numbers all occurrences of 2 numbers next to each others?
- From: "Dana DeLouis" <dana.del at gmail.com>
- Date: Sun, 13 Apr 2008 03:33:52 -0400 (EDT)
> 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. > ...1 followed by a 3, there will be 2 Just to be different for this particular problem... x = {1, 3, 3, 3, 2, 3, 3, 1, 3, 3}; Count[ListConvolve[{3, -3}, x], 0] 4 Count[ListConvolve[{1, -3}, x], 0] 2 -- HTH :>) Dana DeLouis "Nasser Abbasi" <nma at 12000.org> wrote in message news:fti404$ok1$1 at smc.vnet.net... > 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 :) > >