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MathGroup Archive 1997

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Question about Normal[] and O[]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg8537] Question about Normal[] and O[]
  • From: sbecuwe at uia.ua.ac.be (Stefan.Becuwe)
  • Date: Sat, 6 Sep 1997 23:16:08 -0400
  • Sender: owner-wri-mathgroup at wolfram.com

The purpose of Normal[] is to "truncate a power series to give an
ordinary expression".  I hoped it would just remove the O[] term,
but, for one reason or another, it does a bit more (as you can see in
Out[24]).

Question: is there a function that only removes the O[] term
(in Mathematica 2.2? 3.0?)
(I need that "3 - (1 + x)"  and not "2 - x" ...)

If it would have been possible to do a substitution ( /. ) before the
Normal[] function, then the problem would have been solved, but
/. doesn't seem to work when there's an O[] term...



   In[23]:= Series[1+3x^2+x^5,{x,-1,5}]

                                2             3            4          5
   Out[23]= 3 - (1 + x) - 7 (1 + x)  + 10 (1 + x)  - 5 (1 + x)  + (1 + x)  + 
 
             6
   >    O[1 + x]

   In[24]:= Normal[Series[1+3x^2+x^5,{x,-1,5}]] 

                          2             3            4          5
   Out[24]= 2 - x - 7 (1 + x)  + 10 (1 + x)  - 5 (1 + x)  + (1 + x)




Stefan Becuwe


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