Re: Series
- To: mathgroup at smc.vnet.net
- Subject: [mg42675] Re: Series
- From: bobhanlon at aol.com (Bob Hanlon)
- Date: Sun, 20 Jul 2003 06:20:54 -0400 (EDT)
- References: <bfasni$gqh$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Just automate the process that you demonstrated
seriesCap[expr_, n_] :=
Module[{a, sym=
Cases[expr, _Symbol?(!NumericQ[#]&), Infinity]},
Normal[Series[expr /. Thread[sym -> a*sym],
{a, 0, n}]] /. a -> 1];
seriesCap[Sin[x-y^2], 3]
-(x^3/6) + x - y^2
Bob Hanlon
In article <bfasni$gqh$1 at smc.vnet.net>, Konstantin L Kouptsov
<kouptsov at wsu.edu> wrote:
<< When expanding a function of several arguments in series,
I want to retain only terms having the total power not more than some
number. For example:
Series[Sin[x - y^2], {x, 0, 3}, {y, 0, 3}]// Normal// Expand
gives
x - x^3/6 - y^2 + x^2 y^2/2
with the unwanted last term of power 4. How to do this in
elegant/efficient way?
One way is to do
Series[Sin[a x - (a y)^2], {a, 0, 3}] /.{a->1}
but as the function gets more complicated, this way becomes ugly.