用R实现，提取指定时间段对应的其他列数据。

              time                            num
"2017-03-31 14:31:51 CST"     123
"2017-03-31 14:31:51 CST"    456
"2017-03-31 14:31:51 CST"    654
"2017-03-31 14:32:05 CST"     789
"2017-03-31 14:32:05 CST"    548  
"2017-03-31 14:32:05 CST"    987897
"2017-03-31 14:33:58 CST"     65465
"2017-03-31 14:33:58 CST"     8654654
"2017-03-31 14:31:58 CST"     654654
"2017-03-31 14:31:58 CST"    654654
"2017-03-31 14:32:01 CST"     89789
"2017-03-31 14:32:01 CST"     215654
"2017-03-31 14:32:08 CST"    987/8
"2017-03-31 14:32:08 CST"     98789
"2017-03-31 14:32:08 CST"     89789
"2017-03-31 14:32:05 CST"     6565

上面数据表是table1  我想要把time从2017-03-31 14:32:00到2017-03-31 14:33:00对应的num列提取出来，怎么用R实现。

library(lubridate)

date1 <- as.POSIXct("2017-03-31 14:32:00")
date2 <- as.POSIXct("2017-03-31 14:33:00")
int <- new_interval(date1, date2)

df[df$datetime %within% int,]
用lubridate包可以轻松实现，
参考http://stackoverflow.com/questions/19420155/subset-rows-according-to-a-range-of-time