[R] Infinite Series

Bert Gunter bgunter.4567 at gmail.com
Sat Jul 25 01:57:23 CEST 2015


Janh:

It sounds like you really need to go through an R tutorial or two
before posting further, as this is a pretty basic query. Or am I wrong
about this?

An answer: Just use indexing

cumsum(1/seq_len(100)^2)[seq(10, to = 100,by = 10)] ## keeps every 10th

 [1] 1.549768 1.596163 1.612150 1.620244 1.625133 1.628406 1.630750
1.632512 1.633884
[10] 1.634984


But beware FAQ 7.31 for long series.

Cheers,
Bert


Bert Gunter

"Data is not information. Information is not knowledge. And knowledge
is certainly not wisdom."
   -- Clifford Stoll


On Fri, Jul 24, 2015 at 4:37 PM, Janh Anni <annijanh at gmail.com> wrote:
> Hello Jeff,
>
> Thanks a lot.  I tried it and see that it prints out the entire 100 partial
> sums, so I can take the last value as the partial sum for the first 100
> terms. Would there be any way cumsum can print only the nth partial sum,
> i.e. the last value in the array, instead of printing the entire array?
> Thanks again.
>
> Joseph
>
> On Fri, Jul 24, 2015 at 2:02 PM, Jeff Newmiller <jdnewmil at dcn.davis.ca.us>
> wrote:
>
>> Please reply-all so the mailing list stays in the loop.
>>
>> cumsum(1/(1:100)^2)
>>
>> gives you the partial sums up through i=100.
>> ---------------------------------------------------------------------------
>> Jeff Newmiller                        The     .....       .....  Go Live...
>> DCN:<jdnewmil at dcn.davis.ca.us>        Basics: ##.#.       ##.#.  Live
>> Go...
>>                                       Live:   OO#.. Dead: OO#..  Playing
>> Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
>> /Software/Embedded Controllers)               .OO#.       .OO#.  rocks...1k
>> ---------------------------------------------------------------------------
>> Sent from my phone. Please excuse my brevity.
>>
>> On July 24, 2015 10:30:09 AM PDT, Janh Anni <annijanh at gmail.com> wrote:
>> >Hello Jeff,
>> >
>> >Thank you so much for the suggestion,  I searched cumsum as suggested
>> >but
>> >not sure it is what I had in mind.  For instance if I had the infinite
>> >series:    [image: Inline image 1]
>> >
>> >and want to compute the sum of the, say, first 100 terms, how could I
>> >use
>> >cusum to do that?
>> >
>> >Thanks again,
>> >
>> >Janh
>> >
>> >
>> >On Thu, Jul 23, 2015 at 11:51 PM, Jeff Newmiller
>> ><jdnewmil at dcn.davis.ca.us>
>> >wrote:
>> >
>> >> ?cumsum
>> >>
>>
>> >---------------------------------------------------------------------------
>> >> Jeff Newmiller                        The     .....       .....  Go
>> >Live...
>> >> DCN:<jdnewmil at dcn.davis.ca.us>        Basics: ##.#.       ##.#.  Live
>> >> Go...
>> >>                                       Live:   OO#.. Dead: OO#..
>> >Playing
>> >> Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
>> >> /Software/Embedded Controllers)               .OO#.       .OO#.
>> >rocks...1k
>> >>
>>
>> >---------------------------------------------------------------------------
>> >> Sent from my phone. Please excuse my brevity.
>> >>
>> >> On July 23, 2015 8:23:39 PM PDT, Janh Anni <annijanh at gmail.com>
>> >wrote:
>> >> >Dear All,
>> >> >
>> >> >Does anyone know of any R functions that compute partial sums of
>> >> >series?
>> >> >
>> >> >Thanks in advance!
>> >> >
>> >> >Janh
>> >> >
>> >> >       [[alternative HTML version deleted]]
>> >> >
>> >> >______________________________________________
>> >> >R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
>> >> >https://stat.ethz.ch/mailman/listinfo/r-help
>> >> >PLEASE do read the posting guide
>> >> >http://www.R-project.org/posting-guide.html
>> >> >and provide commented, minimal, self-contained, reproducible code.
>> >>
>> >>
>>
>>
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.



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