Hi,

I have the following type of data:

myData <- data.frame(x = 1:5, y = letters[1:5], xDate =
seq(as.Date("2001/2/1"), as.Date("2005/2/1"), by="year") )

> myData
  x y      xDate
  1 a 2001-02-01
  2 b 2002-02-01
  3 c 2003-02-01
  4 d 2004-02-01
  5 e 2005-02-01

What I need is a new column, say xDate2, that for each xDate (or for each
unique combination of x,y, and xDate), I will have few days before and few
days after, as follow:

myData

x y      xDate      xDate2
1 a 2001-02-01   2001-01-30
1 a 2001-02-01   2001-01-31
*1 a 2001-02-01   2001-02-01*  (original row)
1 a 2001-02-01   2001-02-02
1 a 2001-02-01   2001-02-03
2 b 2002-02-01   2002-01-30
2 b 2002-02-01   2002-01-31
*2 b 2002-02-01   2002-02-01*  (original row)
2 b 2002-02-01   2002-02-02
2 b 2002-02-01   2002-02-03
...
5 e 2005-02-01   2005-01-30
5 e 2005-02-01   2005-01-31
*5 e 2005-02-01   2005-02-01 *(original row)
5 e 2005-02-01   2005-02-02
5 e 2005-02-01   2005-02-03

The actual xDate on my data is not as nicely sequenced as the above example.
But the idea is the same, that I would like to get few days before and after
for my each xDate.

I've tried tapply, by and direct assignment like myData$xDate2 <- seq(xDate
- 5, xDate + 5, by="day") and the like, but without result.

Any idea is appreciated.

Thanks much,

Ferry

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