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Re: Conditonal sum

  • To: mathgroup at smc.vnet.net
  • Subject: [mg50269] Re: [mg50263] Conditonal sum
  • From: "David Park" <djmp at earthlink.net>
  • Date: Tue, 24 Aug 2004 06:22:03 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Christopher,

Is this what you mean?

Sm = {1, 3, 4, 7, 11};

a + Plus @@ Sm
26 + a

or

Fold[Plus, a, Sm]
26 + a

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/

From: Christopher Grinde [mailto:christopher.grinde at hive.no]
To: mathgroup at smc.vnet.net

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





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