Try this:
v <- letters; windows <- 5; shift <- 2
e <- embed(v, window)
e[seq(1, nrow(e), shift), window:1]
On Mon, Jun 14, 2010 at 11:46 PM, david hilton shanabrook
<davidshanabr...@me.com> wrote:
> basically I need to create a sliding window in a string. a way to explain
> this is:
>
>> v <-
>> c("a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y")
>> window <- 5
>> shift <- 2
>
> I want a matrix of characters with "window" columns filled with "v" by
> filling a row, then shifting over "shift" and continuing to the next row
> until "v" is exhausted. You can assume "v" will evenly fit "m"
>
> so the result needs to look like this matrix where each row is shifted 2 (in
> this case):
>
>> m
> [,1] [,2] [,3] [,4] [,5]
> [1,] "a" "b" "c" "d" "e"
> [2,] "c" "d" "e" "f" "g"
> [3,] "e" "f" "g" "h" "i"
> [4,] "g" "h" "i" "j" "k"
> [5,] "i" "j" "k" "l" "m"
> [6,] "k" "l" "m" "n" "o"
> [7,] "m" "n" "o" "p" "q"
> [8,] "o" "p" "q" "r" "s"
> [9,] "q" "r" "s" "t" "u"
> [10,] "s" "t" "u" "v" "w"
> [11,] "t" "u" "v" "w" "x"
>
> This needs to be very efficient as my data is large, loops would be too slow.
> Any ideas? It could also be done in a string and then put into the matrix
> but I don't think this would be easier.
>
> I will want to put this in a function:
>
> shiftedMatrix <- function(v, window=5, shift=2){...
>
> return(m)}
>
> thanks
>
> dhs
> [[alternative HTML version deleted]]
>
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