[R] replicate matrix blocks different numbers of times into new matrix

[Ralph S.]

yes, this works, thank yo. very smart solution!

-R
----------------------------------------
> Date: Sat, 19 Jul 2008 19:55:58 -0400
> From: jholtman at gmail.com
> To: ruffel1 at hotmail.com
> Subject: Re: [R] replicate matrix blocks different numbers of times into new matrix
> CC: r-help at r-project.org
> 
> Will this do it:
> 
>> # determine the row numbers of each of the factors
>> x.row <- split(seq(nrow(x)), x[,1])
>> # process the data and replicate the rows
>> result <- lapply(seq_along(x.row), function(.fact){
> +     x[rep(x.row[[.fact]], n[.fact]),]
> + })
>> do.call(rbind, result)
>      [,1] [,2]
> [1,]    1    1
> [2,]    1    3
> [3,]    1    1
> [4,]    1    3
> [5,]    2    4
> [6,]    2    4
>>
> 
> 
> On Sat, Jul 19, 2008 at 7:17 PM, Ralph S.  wrote:
>>
>> Actually not quite - my mistake, since I oversimplified the problem I have.
>>
>> Here is a more realistic x matrix (plus some additional information):
>>
>> # the data
>> x<-matrix(c(1,1,2,1,3,4),3,2)
>>
>> # number of factors
>> n_f<-2
>>
>> # number of rows taken by each factor
>> f_length <- c(2,1)
>>
>> # number of repetitions I want for the first and second factor
>> # actually, always the same factor of expansion: both factors are to be replicated n times
>> n<-c(2,2)
>>
>> I want something like
>>
>> [,1] [,2]
>> [1,] 1 1
>> [2,] 1 3
>> [3,] 1 1
>> [4,] 1 3
>> [5,] 2 4
>> [6,] 2 4
>>
>> but it is only easy to get
>> [,1] [,2]
>> [1,] 1 1
>> [2,] 1 1
>> [3,] 1 3
>> [4,] 1 3
>> [5,] 2 4
>> [6,] 2 4
>>
>> I am not sure about the first target matrix.
>>
>> I could loop through each level of the factor, use a "which(x[,1]==f[k]" to get the row indices for each factor f[k] and then replicate those indices n times and append them to the result for the previous level of the factor. This does not seem efficient, given that I actually have a large matrix with more than 600 factors.
>>
>> Sorry for the initial misspecification - any ideas how I could solve my problem?
>>
>> Best,
>>
>> Ralph
>>
>> ----------------------------------------
>>> Date: Sat, 19 Jul 2008 21:39:25 +0200
>>> From: p.dalgaard at biostat.ku.dk
>>> To: ruffel1 at hotmail.com
>>> CC: r-help at r-project.org
>>> Subject: Re: [R] replicate matrix blocks different numbers of times into new matrix
>>>
>>> Ralph S. wrote:
>>>> Hi,
>>>>
>>>> I am trying to replicate blocks of a matrix (defined by factors) into another matrix, but an unequal, consecutive number of times for each factor.
>>>>
>>>> I need to find an elegant and fast way to do this, so loops will not work.
>>>>
>>>> An example of what I am trying to do is the following:
>>>>
>>>> # the data - first column entries are both data and the two factors
>>>> x<-matrix(c(1,2,3,4),2,2)
>>>>
>>>>> x
>>>>>
>>>> [,1] [,2]
>>>> [1,] 1 3
>>>> [2,] 2 4
>>>>
>>>> # the number of repetitions of the first and second factor
>>>> n<-c(1,3)
>>>>
>>>> This is what I want as output:
>>>>
>>>> [,1] [,2]
>>>> [1,] 1 3
>>>> [2,] 2 4
>>>> [3,] 2 4
>>>> [4,] 2 4
>>>>
>>>>
>>>> Any ideas how to get there? I have tried using tapply with combination of rep, but this does not work (I need 1 and then 3 replications).
>>>>
>> [[elided Hotmail spam]]
>>>>
>>> Will this do?
>>>
>>> x[rep(1:2,n),]
>>>
>>> --
>>> O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B
>>> c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K
>>> (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
>>> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk) FAX: (+45) 35327907
>>>
>>
>> _________________________________________________
>> _________________________________________________________________
>>
>>
>> family_safety_072008
>> ______________________________________________
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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.
>>
> 
> 
> 
> -- 
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
> 
> What is the problem you are trying to solve?

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enger2_072008