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
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