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Re: Extract Integers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg131423] Re: Extract Integers
  • From: Ray Koopman <koopman at sfu.ca>
  • Date: Sun, 21 Jul 2013 21:40:16 -0400 (EDT)
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Cases[equ /. {Plus->List, Times->List, Power->List, 
              Rational[a_,b_]->{a,b}}, _Integer, -1]

{1, 1, 2, 2, 1, 6, 3, 1, 24, 4, 1, 120, 5}

----- Dana DeLouis <dana01 at icloud.com> wrote:
> Hi.  I've run out of ideas.  Does anyone know the proper way to
> extract all the integers from the following simplified version of
> a larger problem I'm working on?
> 
> equ=Series[Exp[x],{x,0,5}] //Normal
> 
> 1+x+x^2/2+x^3/6+x^4/24+x^5/120
> 
> When trying to extract all the integers,
> I understand numbers like 120 are part of Rational[1,120]
> 
> equ //FullForm
> 
> << Not shown here >>
> 
> I thought looking at all LevelSpec was the solution, but apparently not.
> 
> Cases[equ, _Integer, Infinity]
> {1,2,3,4,5}
> 
> (* Or *)
> 
> Position[equ, _Integer, Infinity]
> {{1},{3,2,2},{4,2,2},{5,2,2},{6,2,2}}
> 
> Extract[equ, %]
> {1,2,3,4,5}
> 
> Both ways extract from the numerator, but I just can't seem to extract
> the {2,6,24,120} inside the denominator.
> Does anyone know the proper way?
> Thanks in advance.  :>~
> 
> Dana
> Mac & Math 9



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