On Thu, Apr 14, 2011 at 3:51 AM, mathijsdevaan <mathijsdev...@gmail.com> wrote:
> Hi list, I would like to use the following data.frame to generate matrices
> over a 3 year moving window:
>
> DF = data.frame(read.table(textConnection(" A B C
> 80 8025 1995
> 80 8026 1995
> 80 8029 1995
> 81 8026 1996
> 82 8025 1997
> 82 8026 1997
> 83 8025 1997
> 83 8027 1997
> 84 8026 1999
> 84 8027 1999
> 85 8028 1995
> 85 8029 1998"),head=TRUE,stringsAsFactors=FALSE))
>
> Function to be applied: t(as.matrix(table(DF[,1:2]))) %*%
> as.matrix(table(DF[,1:2]))
>
> I tried this without success:
> n<-rollapply(DF, width = 3, FUN = t(as.matrix(table(DF[,1:2]))) %*%
> as.matrix(table(DF[,1:2])), align = "right")
>
Try this:
Lines <- " A B C
80 8025 1995
80 8026 1995
80 8029 1995
81 8026 1996
82 8025 1997
82 8026 1997
83 8025 1997
83 8027 1997
84 8026 1999
84 8027 1999
85 8028 1995
85 8029 1998"
DF <- read.table(textConnection(Lines), header = TRUE)
f <- function(y) crossprod(table(DF[DF$C %in% y, 1:2]))
years <- sort(unique(DF$C))
e <- as.data.frame(embed(years, 3))
lapply(split(e, e[, 1]), f)
--
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