There is also
> with(daT, tapply(as.character(ObsDate), list(id, ObsSite),
> function(x)format(list(x))))
site1 site4 site5 site7
id1 NA NA NA "06/13/13"
id2 NA NA NA "07/03/14, 05/17/14"
id4 NA "05/08/14" NA NA
id5 NA NA "06/13/14" NA
id6 "05/30/14, 06/28/13" NA NA NA
id7 NA NA "06/25/13" NA
...with the added bonus that if you leave out the format() business, you get a
data structure that doesn't print as nicely, but can be used for further
computations:
> with(daT, tapply(as.character(ObsDate), list(id, ObsSite), list,
> simplify=FALSE))
site1 site4 site5 site7
id1 NULL NULL NULL List,1
id2 NULL NULL NULL List,1
id4 NULL List,1 NULL NULL
id5 NULL NULL List,1 NULL
id6 List,1 NULL NULL NULL
id7 NULL NULL List,1 NULL
> M <- with(daT, tapply(as.character(ObsDate), list(id, ObsSite), list,
> simplify=FALSE))
> M[["id2", "site7"]]
[[1]]
[1] "07/03/14" "05/17/14"
-pd
> On 6 Feb 2020, at 01:37 , Marna Wagley <marna.wag...@gmail.com> wrote:
>
> daT<-structure(list(id = structure(c(1L, 2L, 2L, 3L, 4L, 5L, 5L, 6L
> ), .Label = c("id1", "id2", "id4", "id5", "id6", "id7"), class = "factor"),
> ObsSite = structure(c(4L, 4L, 4L, 2L, 3L, 1L, 1L, 3L), .Label =
> c("site1",
> "site4", "site5", "site7"), class = "factor"), ObsDate =
> structure(c(4L,
> 8L, 2L, 1L, 5L, 3L, 7L, 6L), .Label = c("05/08/14", "05/17/14",
> "05/30/14", "06/13/13", "06/13/14", "06/25/13", "06/28/13",
> "07/03/14"), class = "factor")), .Names = c("id", "ObsSite",
> "ObsDate"), class = "data.frame", row.names = c(NA, -8L))
> daT
> daT$date <- mdy(daT$ObsDate)
--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd....@cbs.dk Priv: pda...@gmail.com
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