将POSIXct日期数量更改为每周的第一天 [英] changing POSIXct date vaules to first day of each week

问题描述

我想使用这些数据（以下）计算每周的平均值 Dist ，同时保留使用 POSIXct 时间类。

  df<  - 结构（list（IndID =结构（c（1L，1L，1L ，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L， ，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L，1L， ，1L，1L，1L），class =factor，.Label =AAA），
 Date = structure（c（1329436800,1329458400,1329480000,1329501600，
 1329523200,1329544800,1329566400， 1329588000,1329609600，
 1329631200,1329652800,1329674400,1329696000,1329717600，
 1329739200,1329760800,1329782400,1329804000,1329825600，
 1329847200,1329868800,1329890400,1329912000,1329933600，
 1329955200,1329976800,1329998400,1330020000,1330041600，
 1330063200,1330084800,1330106400,1330128000,1330149600，
 1330171200,1330192800,1330214400,1330236000,1330257600，
 1330279200,1330300800,1330322400,1330344000,1330365600，
 1330387200,1330408800,1330430400,1330452000,1330473600，
 1330495200），class = c（ POSIXct，POSIXt），tzone =），
 Dist = c（3.85567120344727,52.2649622620809,103.61207930222，
 1352.58506343616,176.911523081261,77.8266318470078,50.3943567710686，
 296.753649985307,70.5826583995618,166.394264991861 ，251.745346701973，
 295.70655057823，44.6664731663839，11.1539274078084，124.578071475754，
 757.728373470112，83.0921234152083，36.6820839851181，29.1406161870034，
 150.442928003814，66.0957159105813，2.23839297570488，184.88312900824，
 513.072526047611，132.868335201626，8.09274857805967，284.479977841835 ，
 479.358187122796,297.273840894826,4.00676616275076,601.492189218489，
 249.001525522847,108.007775719885,28.4035966274261,604.365702677913， 
 1499.59076416313，111.74722960012，25.3528529967124，280.057754683142，
 428.157539641219，70.0365608334965，71.0886617898624，265.823654634254，
 380.247565078552，188.857338305481，9.24402933768915，120.346786301264，
 221.904294953242，201.086079767386，81.7857577639103），DOW = C （5，
 5，6，6，6，6，7，7，7，7，1，1，1，1，2，2，2，2，3，3，
 3 ，3，4，4，4，4，5，5，5，5，6，6，6，6，7，7，7，7，1，
 1,1,1,2,2 ，2,2,3,3,3）），.Names = c（IndID，Date，
Dist，DoW），row.names = c（NA， 50L），class =data.frame）
 
>头（df）
 IndID日期Dist DoW 
 1 AAA 2012-02-16 17:00:00 3.855671 5 
 2 AAA 2012-02-16 23:00:00 52.264962 5 
 3 AAA 2012-02-17 05:00:00 1043.612079 6 
 4 AAA 2012-02-17 11:00:00 1352.585063 6 
 5 AAA 2012-02-17 17:00:00 176.911523 6 
 6 AAA 2012-02-17 23:00:00 77.826632 6 
  

我的以为是要使用 plyr 包来平均每周 Dist ，并且首先要创建一个新的 WeekDate 字段，其中包含每周第一天的日期（不包括时间）。如DoW（星期几）字段所示，数据并不总是在一周的第一天开始。

虽然我似乎没有连接点，我想要每个连续周（DoW 1-7）的最小日期不包括h：m：s）。 >

行1:10将是2012-02-16，
行11:38将是2012-02-19，
行39:50将是2012-02-26

我怀疑 lubridate 包将是有帮助的，但无法得到代码正确。

任何关于特定创建新日期列或更广泛地平均Dist每周的建议或替代方法将不胜感激。

解决方案

使用 plyr ，

 库（lubridate）
库（dplyr）
 df％>％
 group_by（Week = floor_date ，unit =week））％>％
总结（WeeklyAveDist = mean（Dist））
 #Source：本地数据框架[3 x 2] 
＃
＃周WeeklyAveDist 
＃1 2012-02-12 381.7755 
＃2 2012-02-19 252.1116 
＃3 2012-02-26 175.4097 
  / pre> 
 
 
还有 ceiling_date ， round_date  options 。
 
I want to calculate the average Dist for each week using these data (below) while preserving the benefits of a using the POSIXct time class.
    df <- structure(list(IndID = structure(c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L), class = "factor", .Label = "AAA"), 
    Date = structure(c(1329436800, 1329458400, 1329480000, 1329501600, 
    1329523200, 1329544800, 1329566400, 1329588000, 1329609600, 
    1329631200, 1329652800, 1329674400, 1329696000, 1329717600, 
    1329739200, 1329760800, 1329782400, 1329804000, 1329825600, 
    1329847200, 1329868800, 1329890400, 1329912000, 1329933600, 
    1329955200, 1329976800, 1329998400, 1330020000, 1330041600, 
    1330063200, 1330084800, 1330106400, 1330128000, 1330149600, 
    1330171200, 1330192800, 1330214400, 1330236000, 1330257600, 
    1330279200, 1330300800, 1330322400, 1330344000, 1330365600, 
    1330387200, 1330408800, 1330430400, 1330452000, 1330473600, 
    1330495200), class = c("POSIXct", "POSIXt"), tzone = ""), 
    Dist = c(3.85567120344727, 52.2649622620809, 1043.61207930222, 
    1352.58506343616, 176.911523081261, 77.8266318470078, 50.3943567710686, 
    296.753649985307, 70.5826583995618, 166.394264991861, 251.745346701973, 
    295.70655057823, 44.6664731663839, 11.1539274078084, 124.578071475754, 
    757.728373470112, 83.0921234152083, 36.6820839851181, 29.1406161870034, 
    150.442928003814, 66.0957159105813, 2.23839297570488, 184.88312900824, 
    513.072526047611, 132.868335201626, 8.09274857805967, 284.479977841835, 
    479.358187122796, 297.273840894826, 4.00676616275076, 601.492189218489, 
    249.001525522847, 108.007775719885, 2.38435966274261, 604.365702677913, 
    1499.59076416313, 111.74722960012, 25.3528529967124, 280.057754683142, 
    428.157539641219, 70.0365608334965, 71.0886617898624, 265.823654634254, 
    380.247565078552, 188.857338305481, 9.24402933768915, 120.346786301264, 
    221.904294953242, 201.086079767386, 81.7857577639103), DoW = c(5, 
    5, 6, 6, 6, 6, 7, 7, 7, 7, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 
    3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 1, 
    1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3)), .Names = c("IndID", "Date", 
"Dist", "DoW"), row.names = c(NA, -50L), class = "data.frame")

> head(df)
  IndID                Date        Dist DoW
1   AAA 2012-02-16 17:00:00    3.855671   5
2   AAA 2012-02-16 23:00:00   52.264962   5
3   AAA 2012-02-17 05:00:00 1043.612079   6
4   AAA 2012-02-17 11:00:00 1352.585063   6
5   AAA 2012-02-17 17:00:00  176.911523   6
6   AAA 2012-02-17 23:00:00   77.826632   6
My thought was to use the plyrpackage to average Dist by week and wanted to first create a new WeekDate field that contains the date, excluding the time, of the first day of each week.  As seen in the DoW (Day of Week) field, data does not always begin on the first day of the week. 

While i cannot seem to connect the dots, I want the min Date excluding h:m:s) for each sequential week (DoW 1-7).

Rows 1:10 would be 2012-02-16,
    Rows 11:38 would be 2012-02-19,
    Rows 39:50 would be 2012-02-26

I suspect the lubridate package will be helpful but can not get the code correct.  

Any suggestions or alternative methods on the specific creation of a new date column or more broadly averaging Dist for every week would be appreciated.  
解决方案
Using bosom buddy of plyr,  
library(lubridate)
library(dplyr)
df %>% 
  group_by(Week = floor_date(Date, unit="week")) %>% 
  summarize(WeeklyAveDist=mean(Dist))
#Source: local data frame [3 x 2]
#
#        Week WeeklyAveDist
#1 2012-02-12      381.7755
#2 2012-02-19      252.1116
#3 2012-02-26      175.4097
There are also ceiling_date, round_date options.

                        
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