Tena koe David Something like:
matrix(v[1:win + rep(seq(0, (length(v)-5), shift), each=win)], ncol=win, byrow=TRUE) should work (I haven't tested it fully). Note it gives a different answer to your m since I think the last line of your m is incorrect. HTH .... Peter Alspach > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of david hilton shanabrook > Sent: Tuesday, 15 June 2010 3:47 p.m. > To: r-help@r-project.org > Subject: [R] shifted window of string > > 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.
