[R] weighted mean and by() with two index

[Mike Lawrence]

Sounds like a job for plyr: http://had.co.nz/plyr


On Mon, Apr 13, 2009 at 7:56 PM, Dong H. Oh <r.arecibo at gmail.com> wrote:
> Hi expeRts,
>
> I would like to calculate weighted mean by two factors.
>
> My code is as follows:
>
> R> tmp <- by(re$meta.sales.lkm[, c("pc", "sales")],
>                      re$meta.sales.lkm[, c("size", "yr")], function(x)
>                      weighted.mean(x[,1], x[,2]))
>
> The result is as follows:
> R> tmp
> size: micro
> yr: 1994
> [1] 1.090
> ------------------------------------------------------------
> size: small
> yr: 1994
> [1] 1.135
> ------------------------------------------------------------
> size: medium
> yr: 1994
> [1] 1.113
> ------------------------------------------------------------
> size: large
> yr: 1994
> [1] 1.105
> ------------------------------------------------------------
> size: micro
> yr: 1995
> [1] 1.167
> ------------------------------------------------------------
> size: small
> yr: 1995
> [1] 1.096
> ------------------------------------------------------------
> size: medium
> yr: 1995
> [1] 1.056
> ....
> ....
>
> But the form I want to get is as follows:
>            1994       1995         1996      .....
> micro    1.090      1.167         .............
> small     1.135      1.096
> medium 1.113      1.056        .... ........
> large      1.105      ....... ...........
>
> That is, the result should be tabularized.
> How can I get the above form directly? (I don't want to modify tmp with
> as.vector() and matrix() to get the result)
>
> Thank  you in advance.
>
> --------------------------------------------------------------------------
> Donghyun Oh
> CESIS, KTH
> --------------------------------------------------------------------------
>
>        [[alternative HTML version deleted]]
>
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Mike Lawrence
Graduate Student
Department of Psychology
Dalhousie University

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