Re: [R] sequential sum of a vector...

From: denise xifaras <denisexifaras_at_yahoo.com>
Date: Wed, 23 Jul 2008 09:28:30 -0700 (PDT)

Dear Patrizio and all,
Do you know a similar approach to this, so that *any* function is sequentially applied on a matrix? Particularly, instead of wanting to sum columns every 8 rows, how could we apply a linear regression to the columns of a matrix every 8 rows? ie, if we have a matrix say of 100 rows and 3 columns- say columns are price, production cost, desired profit.  How can we apply lm(price~production cost +desired profit) where the data is taken every 10 lines from the matrix, ie we end up with 10 different regressions?  
Any help is welcome,
Thank you very much
Denise
 

From: Patrizio Frederic <frederic.patrizio_at_gmail.com> Subject: Re: [R] sequential sum of a vector... To: "Shubha Vishwanath Karanth" <shubhak_at_ambaresearch.com> Cc: r-help_at_stat.math.ethz.ch
Date: Wednesday, July 23, 2008, 8:30 AM

try this

colSums(matrix(x,8))

regards,

PF

+-------------------------------------------------
| Patrizio Frederic
| Research associate in Statistics,
| Department of Economics,
| University of Modena and Reggio Emilia,
| Via Berengario 51,
| 41100 Modena, Italy
|
| tel:  +39 059 205 6727

| fax: +39 059 205 6947
| mail: patrizio.frederic_at_unimore.it
+-------------------------------------------------


2008/7/23 Shubha Vishwanath Karanth <shubhak_at_ambaresearch.com>:
> Hi R,
>
>
>
> Let,
>
>
>
> x=1:80
>
>
>
> I want to sum up first 8 elements of x, then again next 8 elements of x,
> then again another 8 elements..... So, my new vector should look like:
>
> c(36,100,164,228,292,356,420,484,548,612)
>
>
>
> I used:
>
>
>
> aggregate(x,list(rep(1:10,each=8)),sum)[-1]
>
> or
>
> rowsum(x,group=rep(1:10,each=8))
>
>
>
>
>
> But without grouping, can I achieve the required? Any other ways of
> doing this?
>
>
>
> Thanks, Shubha
>
>
>
> This e-mail may contain confidential and/or privileged i...{{dropped:13}}
>
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>



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