Re: Q: Collect, Coefficient, and non-integer exponents

*To*: mathgroup at smc.vnet.net*Subject*: [mg8759] Re: [mg8733] Q: Collect, Coefficient, and non-integer exponents*From*: Allan Hayes <hay at haystack.demon.co.uk>*Date*: Sun, 21 Sep 1997 20:51:04 -0400*Sender*: owner-wri-mathgroup at wolfram.com

sergio at scisun.sci.ccny.cuny.edu (Sergio Rojas) [mg8733] Q: Collect, Coefficient, and non-integer exponents wants to use Collect and Coefficient on expr = Expand[Sum[(a*n +b*n -c)*x^(n+0.12/n),{n,1,4}]]; He writes: > One knows in advance that a power of x is, for example, 1.12 and > we want to know its coefficient. Apparently Coefficient and Collect > work only with integers. Is there a way to deal with this > situation? Sergio, Coefficient seems to work with inexact exponents in 3.0: Coefficient[expr, x^1.12] a+b-c For Collect, you might try Collect[expr/.x^n_->x^(Round[n/.01]), x]/.x^n_->x^(.01 n) (a + b - c)*x^1.12 + (2*a + 2*b - c)*x^2.06 + (3*a + 3*b - c)*x^3.04 + (4*a + 4*b - c)*x^4.03 Allan Allan Hayes hay at haystack.demon.co.uk http://www.haystack.demon.co.uk/training.html voice:+44 (0)116 2714198 fax: +44 (0)116 2718642 Leicester, UK