Question

我有一个这样的时间序列数据帧给定的一天。

Datetime <- c("2015-09-29 00:00:13", "2015-09-29 00:45:00", "2015-09-29 02:53:20", "2015-09-29 03:22:18", 
              "2015-09-29 05:42:10", "2015-09-29 05:55:50", "2015-09-29 06:14:10", "2015-09-29 07:42:16",
              "2015-09-29 08:31:15", "2015-09-29 09:13:10", "2015-09-29 11:45:14", "2015-09-29 11:56:00", 
              "2015-09-29 13:44:00", "2015-09-29 14:41:20", "2015-09-29 15:33:10", "2015-09-29 15:24:00",
              "2015-09-29 17:24:12", "2015-09-29 17:28:16", "2015-09-29 18:22:34",  
              "2015-09-29 21:34:31", "2015-09-29 22:48:20", "2015-09-29 22:22:22", "2015-09-29 23:38:22")
Measurement <- c(0.6,0.4,0.2,0.5,0.8,0.6,0.7,0.3,0.8,0.8,
                 0.2,0.8,0.2,0.35,0.8,0.4,0.4,0.6,0.1,0.9,
                 0.6,0.2,0.2)

df1 <- data.frame(Datetime,Measurement)

我想将这个数据框子化为4小时窗口并绘制它们，因此得到6个图（12 AM-4AM，4 AM-8AM，8 AM-12PM，12 PM-4PM，4 PM-8PM，8 PM-12AM）。

我这样做是使用data.table将其子集化为12小时窗口（AM＆amp; PM）

setDT(df1)
df1[, `:=`( datetime = as.IDate(Datetime), ante_post = c("AM","PM")[1+(hour(Datetime) >= 12)] ) ]

我想做类似的事情，但是有4小时的窗口，也是数据帧的子集（6个数据帧）。

Answer 1

hour(Datetime)为您提供一个整数（0-23），对应于该事件的小时数。您可以使用整数divisiom（%/%运算符）轻松将数据表子集化为4小时窗口，并使用ggplot2绘制所有内容：

library(ggplot2)
df1[,group:=1+hour(Datetime)%/%4]
qplot(data=df1,x=Datetime,y=Measurement,facets=group~.)

Answer 2

这是一种主要使用cut并通过hour提取lubridate::hour的方法：

library(lubridate)
library(ggplot2)

df1$Datetime <- as.POSIXct(df1$Datetime)

labels_four_hr <- c("12AM - 4AM", "4AM - 8AM", "8AM - 12PM", "12PM - 4PM", "4PM - 8PM", "8PM - 12AM")
labels_six_hr  <- c("12AM - 6AM", "6AM - 12PM", "12PM - 6PM", "6PM = 12AM")

df <- df1 %>%
  mutate(hour = hour(Datetime),
         seg_four_hr = cut(hour, breaks = 0:6 / 6 * 24, include.lowest = TRUE, labels = labels_four_hr),
          seg_six_hr = cut(hour, breaks = 0:4 / 4 * 24, include.lowest = TRUE, labels = labels_six_hr))


ggplot(df, aes(x = Datetime, y = Measurement)) +
  geom_point() +
  facet_wrap(~ seg_four_hr)

ggplot(df, aes(x = Datetime, y = Measurement)) +
  geom_point() +
  facet_wrap(~ seg_six_hr)

如何将给定的时间序列数据集划分为R中的4小时窗口

2 个答案: