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Re: Extract Integers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg131434] Re: Extract Integers
  • From: Fred Simons <f.h.simons at tue.nl>
  • Date: Sun, 21 Jul 2013 21:43:57 -0400 (EDT)
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Hi Dana,

Despite the fact that rational numbers are atoms in Mathematica, pattern 
matching can be used:

In[9]:= Cases[equ, _Integer|_Rational, Infinity] /. 
Rational[a_,b_]->Sequence[a,b]

Out[9]= {1,1,2,2,1,6,3,1,24,4,1,120,5}

Regards,

Fred Simons
Eindhoven University of Technology

Op 21-07-13 10:23, Dana DeLouis schreef:
> 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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