Re: Skipping Elements in Sum
- To: mathgroup at smc.vnet.net
- Subject: [mg61104] Re: Skipping Elements in Sum
- From: Bill Rowe <readnewsciv at earthlink.net>
- Date: Mon, 10 Oct 2005 02:40:06 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
On 10/9/05 at 1:36 AM, qcadesigner at gmail.com wrote:
>Does anyone know how to skip elements using the mathematica sum?
>e.g. take the sum of all i, where i not equal to j.
Yes.
One way to do this with the Sum function would be to use the KroneckerDelta function as follows:
Sum[Subscript[a, n](1 - KroneckerDelta[n, 3]), {n, 5}]
Another way to create the same sum would be
Total[Table[Subscript[a, n], {n, 5}][[Complement[
Range[5], {3}]]]]
and there are many other ways to achieve the same result. Which is best depends on exactly what you are trying to accomplish.
--
To reply via email subtract one hundred and four