R 确保数据帧每天的观测次数最少

考虑下面的数据框

newDat

Date1 <- seq(from = as.POSIXct("2010-05-01 02:00"), 
             to = as.POSIXct("2010-05-02 22:00"), by = 3600)
Dat <- data.frame(DateTime = Date1,
                   x1 = rnorm(length(Date1)))

Date2 <- seq(from = as.POSIXct("2010-05-03 02:00"), 
             to = as.POSIXct("2010-05-03 07:00"), by = 3600)
Dat2 <- data.frame(DateTime = Date2,
                  x1 = rnorm(length(Date2)))

newDat = rbind(Dat,Dat2)

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Date1这里是一个
数据表。表
方法：

library(data.table)
new.dt <- data.table(newDat)
subst <- new.dt[ , if (.N >= 12) x1, by=format(DateTime, "%Y-%m-%d")]

下面是一个
数据表
方法：

library(data.table)
new.dt <- data.table(newDat)
subst <- new.dt[ , if (.N >= 12) x1, by=format(DateTime, "%Y-%m-%d")]