Taylor Series Expansions

*To*: mathgroup at smc.vnet.net*Subject*: [mg32372] Taylor Series Expansions*From*: Joe Helfand <jhelfand at wam.umd.edu>*Date*: Wed, 16 Jan 2002 03:31:08 -0500 (EST)*Organization*: University of Maryland College Park*Sender*: owner-wri-mathgroup at wolfram.com

Wow! I have definitely come to the right place. Thanks for all the responses. Using the Map built in function solved my problem (it still took a bit, so you can imagine what I was dealing with). Here is something else which I have wasted some time on not knowing as much about Mathematica as I should. It has to do with multi-variable Taylor series expansion. Mathematica has a built in Series function. But when you use this for multi-variable functions, it doesn't do quite what I'd expect. Let's say I have a function for two fariables, and I want to expand to 2nd order. When I use Series, it expands each varible to second order, but includes the cross terms, which I want to belong to a 4th order expansion. For example: In[1172]:= Normal[Series[Exp[x y], {x, 0, 2}, {y, 0, 2}]] Out[1172]= \!\(1 + x\ y + \(x\^2\ y\^2\)\/2\) But what I really want is just 1 + x y, where if I go to fourth order, then I'll take the x^2 y^2 / 2. I had to take some time to write some sloppy Taylor series expansion functions that did what I wanted. Is there a way to get around this problem or do you have any suggestions? Thanks Again, Joe

**Follow-Ups**:**Re: Taylor Series Expansions***From:*Daniel Lichtblau <danl@wolfram.com>