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RE: Is it possible to impose a condition on an iterator

  • To: mathgroup at smc.vnet.net
  • Subject: [mg101552] RE: [mg101499] Is it possible to impose a condition on an iterator
  • From: Tomas Garza <tgarza10 at msn.com>
  • Date: Fri, 10 Jul 2009 06:42:55 -0400 (EDT)
  • References: <200907090552.BAA16854@smc.vnet.net>

Quite possible. The straightforward approach would be to take



b = Table[{a=2Ca^2-3 a/(4 a^2)}=2C{a=2C1=2C20}]



and then



Plus@@ (#[[2]]&/@Select[b=2C[Not[6<#[[1]]<12]&])//N


(btw=2C if you wish to sum the elements of a table I suggest you use Plus t=
ogether with Apply - it is much nicer to take advantage of the beauties of =
functional programming) . The above expression has //N at the end in order =
to convert the resulting fraction to a more readable form.



Alternatively=2C



c = Table[a^2-3 a/(4 a^2)=2C{a=2C1=2C20}]



d = Flatten[Position[Range[20]=2C x_/=3Bx<=6||x>=12]]



Plus@@c[[d]]//N



The result in both cases is



2452.73



Tomas



>
> I would like to perform a summation of this type=2C
>
> Sum[a^2 - 3 a/(4 a^2)=2C {a=2C 1=2C 20}]
>
> excluding however some values of the iteratore=2C I would for instance
> like to exclude the values than to greater of 6 and inferior to 12. Is
> it possible?
>
> Thanks
>


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