       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@@ (#[]&/@Select[b=2C[Not[6<#[]<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=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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