Re: Remove the higher order terms in series expansion

*To*: mathgroup at smc.vnet.net*Subject*: [mg52830] Re: Remove the higher order terms in series expansion*From*: David Bailey <dave at Remove_Thisdbailey.co.uk>*Date*: Tue, 14 Dec 2004 05:59:26 -0500 (EST)*References*: <cpjpt7$nob$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

highorder wrote: > I guess this should be simple and hiding somewhere in the manual. Is > there a quick way to remove the high order terms after using > Series[f,{x,x0,n}] command? The problem comes from the output is > actually given by: > > expansion term + O(x^3); > > the O(x^3) should be removed. I will keep trying but wondering if > anyone has a quick answer. > > Thanks. > Hi, The short answer is very quick indeed - just use //Normal - that will remove the O[x]^3 term (note: not O[x^3]). If you want to understand this a little more, look at a series expansion using //FullForm (if in doubt, FullForm is always a good bet) - you will see that there is a special SeriesData structure used - that is why you can't simply remove the O[x]^3 term. Because Mathematica 'remembers' that these things are series, it can do sensible arithmetic on them - for example, you can add or multiply series together keeping track of the number of valid terms in the result. David Bailey dbaileyconsultancy.co.uk