数据 table：对于每一行，从其他 table 生成随机值

Question

我想通过从模拟 table (table_simul) 中生成航班号来模拟航班号，以观察 table 作为基础。

table_simul <- data.table(
  date_f = c("2020-01-01","2020-01-02","2020-01-03","2020-01-03"),
  city = c("Paris","Paris","London", "Berlin")
)

table_obs <- data.table(
  city = c("Paris","Paris","Paris","London","London", "Berlin"),
  flight = c(1,2,7,4,5,14),
  weight = c(0.33,0.33,0.33,0.5,0.5,1)
)

已用数据：

 Table simul:
    
date        city

2020-01-01  Paris
2020-01-01  Paris
2020-01-01  London
2020-01-01  Berlin


Table obs
---------
city   flight   weight

Paris   1        0.33
Paris   2        0.33
Paris   7        0.33
London  4        0.5
London  5        0.5
Berlin  14       1

预期结果：

date_f        city     flight
2020-01-01  Paris       2
2020-01-02  Paris       2
2020-01-03  London      4
2020-01-03  Berlin      14

我想使用数据包table，因为数据量很大。这是我尝试过但没有奏效的方法：

get_flight_sample <- function(param_city){
  table_simul[city==param_city]
  res <- sample(table_obs$flight,1, replace=T, prob = table_obs$weight)
}

res <- table_simul[,.(flight = get_flight_sample(city))]

Answer 1

这样的事情会有帮助吗？

simul_df <- data.frame()
sapply(c(1:1000), FUN = function(datos) {
  date_f = as.character(sample(seq(as.Date('2021/01/01'), as.Date('2022/12/31'), by="day"), 1))
  city = sample(table_obs$city, size = 1)
  flight = sample(table_obs$flight, size = 1)
  weight = sample(table_obs$weight, size = 1)
  simul_df <<- as.data.frame(rbind(simul_df, cbind(date_f, city, flight, weight)))
})

最后你会得到这样的东西：

       date_f   city flight weight
1  2022-06-10 Berlin      7      1
2  2022-12-21  Paris     14   0.33
3  2021-08-12 Berlin     14      1
4  2022-08-30 Berlin      4    0.5
5  2022-06-30  Paris      4      1
6  2021-09-25  Paris      1   0.33
7  2022-08-01  Paris      1    0.5
8  2021-04-17 London     14      1
9  2021-06-11 London      2   0.33
10 2022-11-28 London     14    0.5

您将获得一个数据框，之后您可以将其转换为 data.table。最佳

Answer 2

也许使用辅助函数从 table_obs 中采样，然后加入 table_simul

f <- function(i, ...) {
  if(length(i) == 1) i else sample(i, size = 1, ...)
}

set.seed(42)
tmp <- table_obs[, .(flight = f(flight, prob = weight)), by = city]
table_simul[, flight := tmp[table_simul, on = .(city)]$flight]
table_simul
#       date_f   city flight
#1: 2020-01-01  Paris      1
#2: 2020-01-02  Paris      1
#3: 2020-01-03 London      4
#4: 2020-01-03 Berlin     14

数据 table：对于每一行，从其他 table 生成随机值

data table: for each row generate random values from other table

r

data.table