使用Data.table进行笛卡尔滚动联接

Question

我有两个表：

• dat：包含数据

• 日期：包含日期表

---

library(data.table)

dates = structure(list(date = structure(c(17562, 17590, 17621, 17651, 
                              17682, 17712, 17743, 17774, 17804, 17835, 17865, 17896), class = "Date")), 
      row.names = c(NA, -12L), class = "data.frame")


dat = structure(list(date = structure(c(17546, 17743, 17778, 17901, 
                              17536, 17806, 17901, 17981, 17532, 17722, 17969, 18234), class = "Date"), 
           country = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 3L, 
                                 3L, 3L, 3L), .Label = c("AAA", "BBB", "CCC"), class = "factor"), 
           state = structure(c(1L, 1L, 2L, 3L, 4L, 1L, 2L, 5L, 6L, 1L, 
                               2L, 2L), .Label = c("S1", "S2", "S3", "S4", "S5", "S6"), class = "factor"), 
           item = structure(c(1L, 2L, 4L, 6L, 3L, 5L, 3L, 2L, 2L, 4L, 
                              5L, 7L), .Label = c("M1", "M2", "M3", "M4", "M5", "M6", "M7"
                              ), class = "factor"), value = c(67L, 10L, 50L, 52L, 93L, 
                                                              50L, 62L, 46L, 6L, 30L, 30L, 14L)), row.names = c(NA, -12L
                                                              ), class = "data.frame")


dates = data.table(dates)
dat = data.table(dat)


setkey(dates, date)
setkey(dat, date)

我追求的结果如下。 即与dat的每一行进行滚动连接，然后合并结果。

rbind(
dat[1,][dates, roll = 90],
dat[2,][dates, roll = 90],
dat[3,][dates, roll = 90],
...
dat[12,][dates, roll = 90]
)

我的实际数据集要大得多，因此列出dat的每一行是不实际的。 有没有捷径可做，却没有循环？

Answer 1

如果我正确理解您的意图，则希望将记录翻转90天。 我使用了交叉联接，然后使用过渡标准来进行子集化

您的原始表格：

library(data.table)

dates = structure(list(date = structure(c(17562, 17590, 17621, 17651, 
                                          17682, 17712, 17743, 17774, 17804, 17835, 17865, 17896), class = "Date")), 
                  row.names = c(NA, -12L), class = "data.frame")


dat = structure(list(date = structure(c(17546, 17743, 17778, 17901, 
                                        17536, 17806, 17901, 17981, 17532, 17722, 17969, 18234), class = "Date"), 
                     country = structure(c(1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 3L, 
                                           3L, 3L, 3L), .Label = c("AAA", "BBB", "CCC"), class = "factor"), 
                     state = structure(c(1L, 1L, 2L, 3L, 4L, 1L, 2L, 5L, 6L, 1L, 
                                         2L, 2L), .Label = c("S1", "S2", "S3", "S4", "S5", "S6"), class = "factor"), 
                     item = structure(c(1L, 2L, 4L, 6L, 3L, 5L, 3L, 2L, 2L, 4L, 
                                        5L, 7L), .Label = c("M1", "M2", "M3", "M4", "M5", "M6", "M7"
                                        ), class = "factor"), value = c(67L, 10L, 50L, 52L, 93L, 
                                                                        50L, 62L, 46L, 6L, 30L, 30L, 14L)), row.names = c(NA, -12L
                                                                        ), class = "data.frame")


dates = data.table(dates)
dat = data.table(dat)

注意，我没有设置键。

我正在使用来自参考的交叉连接功能： 如何在R中进行交叉连接？

CJ.table.1 <- function(X,Y)
  setkey(X[,c(k=1,.SD)],k)[Y[,c(k=1,.SD)],allow.cartesian=TRUE][,k:=NULL]

然后我交叉连接，进行滚动连接的子集，重命名列并排序

dsn1<-CJ.table.1(dat,dates)[i.date-date<=90 & i.date-date>=0][,.(date=i.date,country, state, item, value)][order(country, state, item, value,date),]

Answer 2

这不一定是最好的方法，但是您可以在此处简单地编写一个循环来遍历数据：

df <- data.frame()

for (i in 1:nrow(dat)){
    df <- rbind(df, dat[i,][dates, roll = 90])
}

head(df)

          date country state item value
  1: 2018-01-31     CCC    S6   M2     6
  2: 2018-02-28     CCC    S6   M2     6
  3: 2018-03-31     CCC    S6   M2     6
  4: 2018-04-30    <NA>  <NA> <NA>    NA
  5: 2018-05-31    <NA>  <NA> <NA>    NA

编辑：刚看到你说“没有循环”，那已经是漫长的一天。 不过，这是解决问题的一种方法。