For matrices you can use kronecker:
> kronecker(rep(1, 6), data.matrix(Xdf))
[,1] [,2] [,3] [,4]
[1,] 1.1 2.1 3.1 4.1
[2,] 1.2 2.2 3.2 4.2
[3,] 1.1 2.1 3.1 4.1
[4,] 1.2 2.2 3.2 4.2
[5,] 1.1 2.1 3.1 4.1
[6,] 1.2 2.2 3.2 4.2
[7,] 1.1 2.1 3.1 4.1
[8,] 1.2 2.2 3.2 4.2
[9,] 1.1 2.1 3.1 4.1
[10,] 1.2 2.2 3.2 4.2
[11,] 1.1 2.1 3.1 4.1
[12,] 1.2 2.2 3.2 4.2
On Wed, Jan 7, 2009 at 1:08 PM, Ted Harding
<ted.hard...@manchester.ac.uk> wrote:
> On 07-Jan-09 15:22:57, Niccolò Bassani wrote:
>> Dear R users,I'm facing a trivial problem, but I really can't solve it.
>> I've tried a dozen of codes, but I can't get the result I want.
>> The question is: I have a dataframe like this one
>>
>> [,1] [,2] [,3] [,4] [,5]
>> [1,] 1 2 3 4 5
>> [2,] 2 5 5 4 9
>> [3,] 1 6 8 1 2
>> [4,] 8 6 4 1 5
>>
>> made up of decimal numbers, of course.
>> I want to append this dataframe to itself a number x of times, i.e. 3.
>> That is I want a dataframe like this
>>
>> [,1] [,2] [,3] [,4] [,5]
>> [1,] 1 2 3 4 5
>> [2,] 2 5 5 4 9
>> [3,] 1 6 8 1 2
>> [4,] 8 6 4 1 5
>> [5,] 1 2 3 4 5
>> [6,] 2 5 5 4 9
>> [7,] 1 6 8 1 2
>> [8,] 8 6 4 1 5
>> [9,] 1 2 3 4 5
>> [10,] 2 5 5 4 9
>> [11,] 1 6 8 1 2
>> [12,] 8 6 4 1 5
>>
>> I'm searching for an "authomatic" way to do this (I've already used the
>> rbind re-writing x times the name of the frame...), as it must enter a
>> function where one argument is exactly the number x of times to repeat
>> this frame.
>>
>> Any ideas??
>> Thanks in advance!
>> Niccolò
>
> I don't know whether there is anywhere a ready-made function which
> will implement a "rep" paramater for an rbind, but the following ad-hoc
> function will do it for you efficiently (i.e. with the minimum number
> of applications of the rbind() function).
>
> To produce a result which consists of k replicates of x, row-bound:
>
>
> Krbind <- function(x,k){
> y <- x
> if(k==1) return(x)
> p <- floor(log2(k))
> for(i in (1:p)){
> z <- rbind(y,y)
> y <- z
> }
> k <- (k - 2^p)
> if(k==0) return(y) else return(rbind(y,Krbind(x,k)))
> }
>
> ## Example:
>
> Xdf <- data.frame(X1=c(1.1,1.2),X2=c(2.1,2.2),
> X3=c(3.1,3.2),X4=c(4.1,4.2))
>
> Krbind(Xdf,6)
> # X1 X2 X3 X4
> # 1 1.1 2.1 3.1 4.1
> # 2 1.2 2.2 3.2 4.2
> # 3 1.1 2.1 3.1 4.1
> # 4 1.2 2.2 3.2 4.2
> # 5 1.1 2.1 3.1 4.1
> # 6 1.2 2.2 3.2 4.2
> # 7 1.1 2.1 3.1 4.1
> # 8 1.2 2.2 3.2 4.2
> # 9 1.1 2.1 3.1 4.1
> # 10 1.2 2.2 3.2 4.2
> # 11 1.1 2.1 3.1 4.1
> # 12 1.2 2.2 3.2 4.2
>
> Of course, if you're not worried by efficiency, then the simple loop
>
> y <- x
> for(i in (1:(k-1))){y <- rbind(y,x)}
>
> will do it!
>
> Hoping this helps,
> Ted.
>
> --------------------------------------------------------------------
> E-Mail: (Ted Harding) <ted.hard...@manchester.ac.uk>
> Fax-to-email: +44 (0)870 094 0861
> Date: 07-Jan-09 Time: 18:08:14
> ------------------------------ XFMail ------------------------------
>
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