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Re: NSum bug or am I doing something wrong?


On 11/27/08 at 5:33 AM, ebpr08 at gmail.com (Ebpr Preb) wrote:

>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?

Use Chop, e.g.

In[5]:= Chop@NSum[(-1)^(k + 1)*(.2)^k, {k, 1, 32}]

Out[5]= 0.166667


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