dplyr 代码 "df %>% group_by(date = cut(date, breaks = "1 hour"))" 不再产生预期的结果？答案

【问题标题】：dplyr code "df %>% group_by(date = cut(date, breaks = "1 hour"))" no longer produces the desired result?dplyr 代码 "df %>% group_by(date = cut(date, breaks = "1 hour"))" 不再产生预期的结果？
【发布时间】：2018-02-21 10:00:45
【问题描述】：

我一直在使用以下 dplyr 代码从 1 分钟的时间序列数据中生成每小时平均值。该代码已经运行了几个月，但最近产生了一些有问题的结果。是否对以下任何函数进行了更改：group_by()、cut() 或 summarise()？

df <- structure(list(date = structure(c(1505187300, 1505187360, 1505187420, 1505187480, 1505187540, 1505187600, 1505187660, 1505187720, 1505201580, 1505201640), class = c("POSIXct", "POSIXt"), tzone = "UTC"), co = c(0.149,0.149,0.149, 0.106, 0.149, 0.149, 0.192, 0.149, 0.149, 0.149), co2 = c(544L, 545L, 544L, 543L, 546L, 546L, 548L, 547L, 549L, 554L), VOC = c(22.55, 22.55, 22.8198, 23.2602, 22.9501, 23.2154, 23.4262, 23.0231, 23.0525, 22.7911), RH = c(77.02, 76.9, 77.2, 76.6, 76.99, 76.83, 77.13, 77.81, 77.48, 77.1), ugm3 = c(12.862, 13.408, 14.188, 12.342, 13.278, 12.81, 10.834, 13.018, 12.992, 12.498), temp = c(62.06, 62.02, 62.02, 61.98, 61.94, 61.9, 61.86, 61.78, 61.8, 61.8)), .Names = c("date", "co", "co2", "VOC", "RH", "ugm3", "temp"), row.names = c(NA, 10L), class = "data.frame")

new_df <- df %>% 
    group_by(date = cut(date, breaks = "1 hour")) %>%
    summarize(co = mean(co), co2 = mean(co2), VOC = mean(VOC), RH = mean(RH), ugm3 = mean(ugm3), temp = mean(temp))

new_df

预期输出：

expected_output <- structure(list(date = structure(c(1L, 5L), .Label = c("2017-09-12 03:00:00", "2017-09-12 04:00:00", "2017-09-12 05:00:00", "2017-09-12 06:00:00", "2017-09-12 07:00:00"), class = "factor"), co = c(0.149, 0.149), co2 = c(545.375, 551.5), VOC = c(22.97435, 22.9218), RH = c(77.06, 77.29), ugm3 = c(12.8425, 12.745), temp = c(61.945, 61.8)), class = c("tbl_df", "tbl", "data.frame"), .Names = c("date", "co", "co2", "VOC", "RH", "ugm3", "temp"), row.names = c(NA, -2L))

实际输出：

actual_output <- structure(list(co = 0.149, co2 = 546.6, VOC = 22.96384, RH = 77.106, ugm3 = 12.823, temp = 61.916), .Names = c("co", "co2", "VOC", "RH", "ugm3", "temp"), class = "data.frame", row.names = c(NA, -1L))

在本周之前，此代码会生成一个新的 df，其中包含两个观察结果，一个针对 03:00:00 小时，另一个针对 07:00:00 小时。虽然group_by() 函数似乎正确分配了新的每小时时间戳，但summarize() 函数的行为不正常。任何见解都值得赞赏。谢谢！

如果有更强大的替代方法可以将时间序列数据聚合到特定间隔，我会全力以赴！

【问题讨论】：

我得到了你的预期输出，你能分享一下你得到了什么吗？
好像group_by被跳过了
尝试用dplyr::group_by替换group_by
和summarizedplyr::summarize
我打赌你在dplyr之后加载了plyr;)

标签： r datetime group-by dplyr summarize

【解决方案1】：

您在dplyr 之后加载了plyr。

library(dplyr)
# ...
library(plyr)
# ------------------------------------------------------------------------------# -------------------------------------------
# 
# Attachement du package : ‘plyr’
# 
# The following objects are masked from ‘package:dplyr’:
# 
#     arrange, count, desc, failwith, id, mutate, rename, summarise, summarize

我们应该始终阅读这些警告 :)。现在让我们看看会发生什么：

df %>% 
   group_by(date = cut(date, breaks = "1 hour")) %>%
   summarize(co = mean(co), co2 = mean(co2), VOC = mean(VOC), RH = mean(RH), ugm3 = mean(ugm3), temp = mean(temp))
#     co   co2      VOC     RH   ugm3   temp
# 1 0.149 546.6 22.96384 77.106 12.823 61.916

如果您在plyr 之后加载dplyr，或使用dplyr::summarize，您将获得预期的行为。

df %>% 
   group_by(date = cut(date, breaks = "1 hour")) %>%
   dplyr::summarize(co = mean(co), co2 = mean(co2), VOC = mean(VOC), RH = mean(RH), ugm3 = mean(ugm3), temp = mean(temp))
# # A tibble: 2 x 7
#                  date    co     co2      VOC    RH    ugm3   temp
#                <fctr> <dbl>   <dbl>    <dbl> <dbl>   <dbl>  <dbl>
# 1 2017-09-12 03:00:00 0.149 545.375 22.97435 77.06 12.8425 61.945
# 2 2017-09-12 07:00:00 0.149 551.500 22.92180 77.29 12.7450 61.800

【讨论】：