I am trying to use data.tablefor an operation that I do not do, if for data.table. Suppose I have the following
set.seed(1)
id<-rep(LETTERS[1:6], each=3)
event<-rep(letters[1:4], each=3, length.out=18)
order<-rep(1:3, 6)
var<-rnorm(18)
dt<-data.table(id, event, order, var)
setkey(dt, id)
id event order var
1: A a 1 -0.62645381
2: A a 2 0.18364332
3: A a 3 -0.83562861
4: B b 1 1.59528080
5: B b 2 0.32950777
6: B b 3 -0.82046838
7: C c 1 0.48742905
8: C c 2 0.73832471
9: C c 3 0.57578135
10: D d 1 -0.30538839
11: D d 2 1.51178117
12: D d 3 0.38984324
13: E a 1 -0.62124058
14: E a 2 -2.21469989
15: E a 3 1.12493092
16: F b 1 -0.04493361
17: F b 2 -0.01619026
18: F b 3 0.94383621
and I need to calculate in the new column the Euclidean distance between the values of var, having different idbut identical event, supporting the orderobservational data .
I realized that using the command byin the expression, data.tableI divide the data into pieces that I can use in connection with other fragments from another data.table, but can I do the same thing in the same one data.table?
To be clear, this is what I would like to get
id event order var euclid
1: A a 1 -0.62645381 3.097720
2: A a 2 0.18364332 3.097720
3: A a 3 -0.83562861 3.097720
4: B b 1 1.59528080 2.433635
5: B b 2 0.32950777 2.433635
6: B b 3 -0.82046838 2.433635
7: C c 1 0.48742905 NA
8: C c 2 0.73832471 NA
9: C c 3 0.57578135 NA
10: D d 1 -0.30538839 NA
11: D d 2 1.51178117 NA
12: D d 3 0.38984324 NA
13: E a 1 -0.62124058 3.097720
14: E a 2 -2.21469989 3.097720
15: E a 3 1.12493092 3.097720
16: F b 1 -0.04493361 2.433635
17: F b 2 -0.01619026 2.433635
18: F b 3 0.94383621 2.433635
Many thanks!
source
share