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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