Extracting Coefficients and Powers

*To*: mathgroup at smc.vnet.net*Subject*: [mg48254] Extracting Coefficients and Powers*From*: "Bruce W. Colletti" <bcolletti at compuserve.com>*Date*: Wed, 19 May 2004 05:20:50 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

I have a sum of terms, each of the form "a * x^r" or "a * 1/x^r", where a and (positive) r are real numbers (if a is missing, it's presumably 1 or -1 and if there is no x-term, r is understood to be 0). In my application, the complete expression is given by Expand[p], where p is a product of terms having form a t^b + c t^d (p is actually a factorial moment generating function). I want to extract all coefficients into a list (including 1 or -1 coefficients), and exponents into another (to include 0 for any constant term). For instance, x^3.2 + 5 - 3 / x^5.2 - x^5 yields the coefficients' list {1, 5, -3, -1} and exponents' list {3.2, 0, -5.2,5}. How would I build these lists? Must Cases[ ] be used or are there built-in functions? Thanks. Bruce

**Follow-Ups**:**Re: Extracting Coefficients and Powers***From:*Daniel Lichtblau <danl@wolfram.com>