加入與timeintervals R中

Question

高效的方式，我有一個表（1）所示：

START;END;CATEGORY 
20.05.2017 19:23:00;20.05.2017 19:27:00;A 
20.05.2017 19:27:00;20.05.2017 19:32:00;B 
20.05.2017 19:32:00;20.05.2017 19:38:00;A 

和表（2）所示：

TIMESTAMP;VALUES 
20.05.2017 19:24:09;323 
20.05.2017 19:23:12;2322 
20.05.2017 19:27:55;23333 
20.05.2017 19:36:12;123123 

現在我要加入類別從表1到表2.關鍵是時間戳。如果表2中的TIMESTAMP在table1的START和END之間添加類別。我想基本上是一個表是這樣的：

TIMESTAMP;VALUES;CATEGORY 
20.05.2017 19:24:09;323;A 
20.05.2017 19:23:12;2322;A 
20.05.2017 19:27:55;23333;B 
20.05.2017 19:36:12;123123;B 

---

這是我的嘗試，但他們效率不高：

I）

for(j in seq(dim(table1)[1])){ 
    for(i in seq(dim(table2)[1])){ 
    table2[table2$TIMESTAMP[i]>=table1$START[j] & table2$TIMESTAMP[i]<=table1$END[j]] <- table1$CATEGORY[j] 
    } 

II）

mapped_df <- data.frame() 
for(i in seq(dim(table1)[1])){ 
    start <- as.POSIXct(table1$START[i]) 
    end <- as.POSIXct(table1$END[i]) 
    cat <- table1$CATEGORY[i] 
    mapped_df <- rbind(mapped_df, data.frame(TIMESTAMP=seq(from=start, by=1, to=end), CATEGORY=cat)) 
} 

merge(table2 , mapped_df) 

在此先感謝！

Answer 1

我傾向於使用SQL來執行此操作。 sqldf包派上用場。

Table1 <- 
    structure(
    list(START = structure(c(1495322580, 1495322820, 1495323120), 
          class = c("POSIXct", "POSIXt"), 
          tzone = ""), 
     END = structure(c(1495322820, 1495323120, 1495323480), 
         class = c("POSIXct", "POSIXt"), 
         tzone = ""), 
     CATEGORY = c("A", "B", "A")), 
    class = "data.frame", 
    .Names = c("START", "END", "CATEGORY"), 
    row.names = c(NA, -3L) 
) 

Table2 <- 
    structure(
    list(TIMESTAMP = structure(c(1495322649, 1495322592, 1495322875, 1495323372), 
           class = c("POSIXct", "POSIXt"), 
           tzone = ""), 
    VALUES = c(323L, 2322L, 23333L, 123123L)), 
    class = "data.frame", 
    .Names = c("TIMESTAMP", "VALUES"), 
    row.names = c(NA, -4L)) 

library(sqldf) 

sqldf("SELECT T2.TIMESTAMP, T2.[VALUES], T1.CATEGORY 
     FROM Table2 T2 
      LEFT JOIN Table1 T1 
      ON T2.TIMESTAMP > T1.START AND T2.TIMESTAMP < T1.END")