Mathematica 9 is now available
Student Support Forum
-----
Student Support Forum: 'Power series in multiple variables' topicStudent Support Forum > General > "Power series in multiple variables"

< Previous Comment | Next Comment >Help | Reply To Comment | Reply To Topic
Author Comment/Response
Eric Harley
10/12/05 08:25am

Well, I guess I answered my own question. I'm posting what I have come up with in case it's useful for anyone else.

I chose to use this approach (using the Exponent[] function) because it allows the resulting function to be much more flexible than I could figure out how to do with my own pattern matching. It can easily be used with specific variables, it includes stuff in the denominator of fractions, etc.

Clear[polyOrder];
polyOrder = Function[{poly, varlist, ord},
Block[{termsList, orderList, selTerms},
termsList = List @@ poly;
orderList = Exponent[#, varlist, List] & /@ termsList;
orderList = Map[Flatten, orderList, 2];
orderList = Apply[Plus, orderList, 2];
termsList = Transpose[{termsList, orderList}];
selTerms = Select[termsList, #〚2〛 ≤ ord &];
Plus @@ (#〚1〛 & /@ selTerms)
]
];

Note that poly isn't the direct result of the Series[] function in the question. You should do //Normal//Expand on it to get rid of the O[] terms and all the factoring.

varlist should always be in list form, like {x} or {x,y,z}.

ord is just a number, the order of the product of the variables in varlist for any given term.

URL: ,

Subject (listing for 'Power series in multiple variables')
Author Date Posted
Power series in multiple variables Eric Harley 10/11/05 11:34am
Re: Power series in multiple variables Eric Harley 10/12/05 08:25am
Re: Power series in multiple variables Eric Harley 10/14/05 09:19am
Re: Power series in multiple variables Carbaboran 01/25/12 06:53am
< Previous Comment | Next Comment >Help | Reply To Comment | Reply To Topic