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Re: Extract Integers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg131432] Re: Extract Integers
  • From: Bob Hanlon <hanlonr357 at gmail.com>
  • Date: Sun, 21 Jul 2013 21:43:17 -0400 (EDT)
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  • References: <20130721082357.762536A19@smc.vnet.net>

equ = Series[Exp[x], {x, 0, 5}] // Normal;


{Cases[equ, _Integer, Infinity],
   Cases[equ, Rational[n_, d_] :> {n, d}, Infinity]} // Flatten // Union


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


Cases[equ, i_Integer | Rational[n_, d_] :> Sequence[i, n, d],
  Infinity] // Union


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



Bob Hanlon


On Sun, Jul 21, 2013 at 4:23 AM, 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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