RE: NSum bug or am I doing something wrong?

*To*: mathgroup at smc.vnet.net*Subject*: [mg93895] RE: [mg93869] NSum bug or am I doing something wrong?*From*: "David Park" <djmpark at comcast.net>*Date*: Fri, 28 Nov 2008 05:06:20 -0500 (EST)*References*: <11687945.1227782105568.JavaMail.root@m02>

In these cases people usually use Chop. But it does seem like a slight bug that an imaginary component gets in. Why not make your do-it-yourself NSum? Total[(k \[Function] (-1)^(k + 1) .2^k) /@ Range[32]] 0.166667 It actually seems to run faster than NSum. David Park djmpark at comcast.net http://home.comcast.net/~djmpark From: Ebpr Preb [mailto:ebpr08 at gmail.com] Hi, I'm getting imaginary answers for simple NSums of rational numbers. The example below produces the issue in Mathematica 7: NSum[(-1)^(k + 1)*(.2)^k, {k, 1, 32}] gives me the result: 0.166667 + 1.1972*10^-44 I When I switch to Sum the problem disappears. Any hint? Thanks so much. ebpr