Hi
Thanks for providing data. I did not see any response and frankly speaking I do
not use data.table so I am not sure what do you mean by lagging t1.
I would start with ordering data.
ooo<-order(data$id, data$year)
data <- data[ooo,]
Then you can split data according to id.
datas<-split(data[,c(1,3)], data$id)
dput(head(datas))
structure(list(`28954` = structure(list(year = c(2005, 2006,
2007, 2008), t1 = c(-1.81807494163513, -1.81807494163513, -1.81807494163513,
-1.81807494163513)), .Names = c("year", "t1"), row.names = c(58L,
45L, 35L, 46L), class = "data.frame"), `28955` = structure(list(
year = c(2005, 2006, 2007, 2008), t1 = c(-1.81807494163513,
-1.81807494163513, -1.81807494163513, -1.81807494163513)), .Names =
c("year",
"t1"), row.names = c(59L, 70L, 69L, 72L), class = "data.frame"),
`28956` = structure(list(year = c(2005, 2006, 2007, 2008),
t1 = c(-1.81807494163513, -1.81807494163513, -1.81807494163513,
-1.81807494163513)), .Names = c("year", "t1"), row.names = c(53L,
66L, 74L, 51L), class = "data.frame"), `28957` = structure(list(
year = c(2005, 2006, 2007, 2008), t1 = c(-1.81807494163513,
-1.81807494163513, -1.81807494163513, -1.81807494163513
)), .Names = c("year", "t1"), row.names = c(71L, 64L,
54L, 24L), class = "data.frame"), `28958` = structure(list(
year = c(2005, 2006, 2007, 2008), t1 = c(-1.81807494163513,
-1.81807494163513, -1.81807494163513, -1.81807494163513
)), .Names = c("year", "t1"), row.names = c(34L, 27L,
1L, 31L), class = "data.frame"), `28959` = structure(list(
year = c(2005, 2006, 2007, 2008), t1 = c(-1.81807494163513,
-1.81807494163513, -1.81807494163513, -1.81807494163513
)), .Names = c("year", "t1"), row.names = c(17L, 18L,
30L, 44L), class = "data.frame")), .Names = c("28954", "28955",
"28956", "28957", "28958", "28959"))
But now I am lost what result you expect. Can you explain it on this smaller
data set?
Cheers
Petr
> -----Original Message-----
> From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Janka
> VANSCHOENWINKEL
> Sent: Monday, September 07, 2015 1:18 PM
> To: r-help@r-project.org
> Subject: [R] Lag variable by group
>
> Hi!
>
> I have the following dataset with the variables ID (this is a unique ID
> per farmer), year, and another variable t1.
> I now would like to have a fourth variable which is the lag value of t1
> for each farm ID.
>
> I found a code on the internet that does exactly what I need, but it
> does not work for this dataset. Does anyone have suggestions about how
> I can make this work?
>
> Thanks a lot!
>
> Janka
>
> data<-structure(list(year = c(2007, 2005, 2008, 2006, 2005, 2007, 2006,
> 2008, 2007, 2005, 2007, 2007, 2005, 2006, 2005, 2006, 2005, 2006, 2007,
> 2007, 2005, 2008, 2007, 2008, 2005, 2005, 2006, 2008, 2007, 2007, 2008,
> 2008, 2006, 2005, 2007, 2006, 2008, 2008, 2007, 2007, 2007, 2006, 2006,
> 2008, 2006, 2008, 2008, 2008, 2006, 2007, 2008, 2007, 2005, 2007, 2008,
> 2005, 2007, 2005, 2005, 2008, 2005, 2006, 2005, 2006, 2008, 2006, 2008,
> 2006, 2007, 2006, 2005, 2008, 2006, 2007, 2008, 2006, 2006, 2006, 2005,
> 2008, 2006, 2008, 2006, 2006, 2006, 2007, 2008, 2005, 2007, 2006, 2007,
> 2008, 2006, 2008, 2005, 2007, 2005, 2007, 2006, 2006), id = c(28958L,
> 28962L, 28962L, 28965L, 28960L, 28962L, 28964L, 28970L, 28961L, 28965L,
> 78458L, 28960L, 28961L, 28961L, 28969L, 28962L, 28959L, 28959L, 58845L,
> 28965L, 28963L, 78459L, 28967L, 28957L, 28964L, 28966L, 28958L, 28960L,
> 28969L, 28959L, 28958L, 28969L, 58845L, 28958L, 28954L, 28963L, 78458L,
> 28965L, 28966L, 28963L, 28970L, 28970L, 28960L, 28959L, 28954L, 28954L,
> 58845L, 28967L, 28966L, 78459L, 28956L, 28964L, 28956L, 28957L, 28961L,
> 28970L, 28968L, 28954L, 28955L, 28968L, 28968L, 28967L, 28967L, 28957L,
> 28966L, 28956L, 28964L, 28969L, 28955L, 28955L, 28957L, 28955L, 28968L,
> 28956L, 28963L, 29004L, 58848L, 29005L, 28974L, 29005L, 28974L, 29006L,
> 28981L, 29007L, 29002L, 28980L, 29001L, 29006L, 29005L, 28989L, 28989L,
> 58846L, 28980L, 28981L, 78467L, 28990L, 28973L, 29004L, 28972L,
> 29006L), t1 = c(-1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.81807494163513, -1.81807494163513, -
> 1.81807494163513, -1.43884992599487, -1.43884992599487, -
> 1.43884992599487, -1.43884992599487, -1.43884992599487, -
> 1.43884992599487, -1.43884992599487, -1.43884992599487, -
> 1.43884992599487, -1.43884992599487, -1.43884992599487, -
> 1.43884992599487, -1.43884992599487, -1.43884992599487, -
> 1.43884992599487, -1.43884992599487, -1.43884992599487, -
> 1.43884992599487, -1.43884992599487, -1.43884992599487, -
> 1.43884992599487, -1.43884992599487, -1.43884992599487, -
> 1.43884992599487, -1.43884992599487)), .Names = c("year", "id", "t1"),
> row.names = c(NA, 100L), class = "data.frame")
>
> library(data.table)
> data[, lag.t1:=c(NA, t1[-.N]), by=id]
>
>
> Thank you very much!
>
> Janka
>
> [[alternative HTML version deleted]]
>
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