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Re: bimodal distribution in sign of difference of Pi digits]

  • To: mathgroup at
  • Subject: [mg51725] Re: bimodal distribution in sign of difference of Pi digits]
  • From: Roger Bagula <tftn at>
  • Date: Sun, 31 Oct 2004 01:15:46 -0500 (EST)
  • Reply-to: tftn at
  • Sender: owner-wri-mathgroup at

Dear jasonp,
I don't know.
This method is a new way to investigate Pi digits.
I had done some counts of base ten digits frequencies before this.
I have no real explaination of why the difference is higher in higher number of digits. 
 The groups of positive "Sign"s should
random. It is Sign[x]-> {-1,0,1} depending on the difference in consecutive
differences. It is the probability of a digit pair:
 {a,b}--> Sign[a-b]
p=Probability [a]*Probability[b]
If they are equal as p0:
If the Mathematica for such a probability would be:
p0->Random[Integer,{0,9}] as a Distribution
Since this is an straight type probabilty and not a Gaussian
the probabilies are equal and should be over a long term
1/10 each or a total of
different for different combinations:
at {4/10,4/10,2/10} that gives something like
I'm not seeing that kind of behavior except for the bimodal
which is expected as
 (a=b) is
only about 2/10 of the 1/100 and I'm seeing more zeros than that.
It appears to be a much more complex distribution.
I want to try E and orther irrational numbers by this method as well!
I'm glad you asked as I hadn't thought to do a probability analysis 
until now!
I can simulate the probability above in Mathematica
 and see what I get
 and compare them.
jasonp at wrote:

>Quoting Roger Bagula :
>  >
>>(* Sum of the sign of the differences between the first 2000 digits of Pi*)
>>    >>
>Shouldn't this behave like a random walk, i.e. the variance
>increases over time?
>This message was sent using's Webmail.
>  >

Respectfully, Roger L. Bagula
tftn at, 11759Waterhill Road, Lakeside,Ca 92040-2905,tel: 619-5610814 :
alternative email: rlbtftn at

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