轉換數據幀到時間序列在30分鐘間隔

Question

隨着

x <- data.frame(value = round(rt(20, 2), 2), 
       time = c("2012-09-03 00:00:00", "2012-09-03 00:30:00", 
         "2012-09-03 01:00:00", "2012-09-03 01:30:00", 
         "2012-09-03 02:00:00", "2012-09-03 02:30:00", 
         "2012-09-03 03:00:00", "2012-09-03 03:30:00", 
         "2012-09-03 04:00:00", "2012-09-03 04:30:00", 
         "2012-09-03 05:00:00", "2012-09-03 05:30:00", 
         "2012-09-03 06:00:00", "2012-09-03 06:30:00", 
         "2012-09-03 07:00:00", "2012-09-03 07:30:00", 
         "2012-09-03 08:00:00", "2012-09-03 08:30:00", 
         "2012-09-03 09:00:00", "2012-09-03 09:30:00")) 

有一種方法將其與30分鐘的間隔轉換爲時間序列的格式？如：

  00:00:00 00:30:00 01:00:00 01:30:00 02:00:00 02:30:00 ... 
2012-09-03  0.31 -1.01  0.94 -0.75 -0.40  0.41 

事實上，有一天以上的數據，我只是展示了它的一部分。謝謝！

Answer 1

library(plyr) 
library(reshape2) 
x2 <- cbind(x, ldply(strsplit(x$time, " ")))[-2] 
names(x2) <- c("value", "date", "time") 
dcast(x2, date~time)