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]] > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.