您可以使用 data.table

You can use dcast from data.table

library(data.table)
dcast(dT, A + B + ID ~ paste0("E", rowid(ID)))
#   A  B ID        E1        E2        E3
#1 a1 b1  1 0.4069439 0.3526222 0.2337894
#2 a1 b2  3 0.6211421 0.3943915 0.5505793
#3 a2 b2  4 0.7421095 0.7796073 0.6906605

您需要先创建正确的时间变量，即 rowid（ ID）。

You need to create the correct 'time variable' first which is what rowid(ID) does.