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Re: Conditonal sum

• To: mathgroup at smc.vnet.net
• Subject: [mg50285] Re: [mg50263] Conditonal sum
• From: "Wolf, Hartmut" <Hartmut.Wolf at t-systems.com>
• Date: Tue, 24 Aug 2004 06:22:36 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

>-----Original Message-----
>From: Christopher Grinde [mailto:christopher.grinde at hive.no]
To: mathgroup at smc.vnet.net
>Sent: Monday, August 23, 2004 12:35 PM
>To: mathgroup at smc.vnet.net
>Subject: [mg50285] [mg50263] Conditonal sum
>
>
>I am new to mathematica and could really need a tip on how to 
>implement a 
>conditional sum.  Pseudocode would be something like this
>
>
>EndSum=a;
>if j in Sm:
>	EndSum=EndSum+f[j]
>end
>
>
>I have tried doing this by using an If-clause inside the 
>sum-function, but  
>
>this seems little elegant and is nor very suitable for 
>symbolic calculations.
>
>Any advice would be highly appreciated
>
>Christopher Grinde
>
>

Don't quite understand your case, just guessing, would

   Plus @@ f /@ Sm 

do it?

--
Hartmut