r - xts 微秒问题

Question

在 .RData 文件中保存了一个 xts 对象，然后在另一个 R 实例中再次打开它。我丢失了微秒时间戳。我在两个环境中都保留了相同的配置，包括digits.secs=6。

yum <- structure(c(262, 262, 262, 100, 100, 100, 120, 370, 370, 370, 367, 392), 
                 class = c("xts", "zoo"), 
                 .indexCLASS = c("POSIXct", "POSIXt"), 
                 tclass = c("POSIXct", "POSIXt"), 
                 .indexTZ = "UTC", tzone = "UTC", 
                 index = structure(c(1355821310.69496, 
                                    1355821310.73023, 1355821310.75223, 
                                    1355821310.8355, 1355821310.87186,
                                    1355821310.88684), 
                 tzone = "UTC", 
                 tclass = c("POSIXct", "POSIXt")), 
                 .Dim = c(6L, 2L), 
                 .Dimnames = list(NULL, c("SzX", "SzS")
                )
              )

任何指针？