Re: Sum question and general comment

*To*: mathgroup at smc.vnet.net*Subject*: [mg50700] Re: Sum question and general comment*From*: Bill Rowe <readnewsciv at earthlink.net>*Date*: Fri, 17 Sep 2004 01:16:36 -0400 (EDT)*Sender*: owner-wri-mathgroup at wolfram.com

On 9/15/04 at 1:49 AM, stevebg at adelphia.net (Steve Gray) wrote: >I find no way to do, for example, "Sum over i=1 to 100 except i!= >23 and 36", etc., An obvious way would be to express this as three sums, i.e., Sum[f,{i,22}]+Sum[f,{i,24,35}]+Sum[f,{i,37,100}] >or Sum over values belonging to a list, such as >"Sum over i (belonging to) {1,2,3,5,7,8,21}", etc., This is easily done as one of the following Plus@@(f/@list) Total[f/@list] Tr[f/@list] where list is the list of values you want to sum over In fact, this same technique can be used to solve your first problem as well, i.e. Total[f/@Complement[Range[100],{23,36}]] -- To reply via email subtract one hundred and four