将数据拆分或子集为 30 分钟的时间间隔 [英] split or subset data into 30 minute intervals

问题描述

我有一个如下形式的数据框:

I have a data frame of the following form:

Temp    Depth      Light   x   time date                   time.at.depth
104     18.59      -2.7    27 21:38 2012-06-20             4
109     18.59      -2.7    27 22:02 2012-06-20             5
110     18.75      -4.0    27 22:07 2012-06-20             5
113     18.91      -2.7    27 22:21 2012-06-20             4
114     18.91      -4.0    27 22:26 2012-06-20             5
115     18.91      -2.7    27 22:31 2012-06-20             5
117     18.91      -2.7    27 22:40 2012-06-20             4
118     18.75      -4.0    27 22:45 2012-06-20             5
119     18.75      -2.7    27 22:50 2012-06-20             5
121     18.59      -4.0    27 22:59 2012-06-20             4
122     18.75      -2.7    27 23:04 2012-06-20             5
123     18.75      -4.0    27 23:09 2012-06-20             5
126     18.59      -2.7    27 23:23 2012-06-20             5
127     18.59      -2.7    27 23:28 2012-06-20             5
128     18.59      -4.0    27 23:33 2012-06-20             5
133     18.75      -4.0    27 23:57 2012-06-20             5
136     18.59      -4.0    27 00:11 2012-06-20             5
138     18.59      -2.7    27 00:21 2012-06-20             5
140     18.91      -2.7    27 00:30 2012-06-20             5

我想将数据子集划分为 30 分钟的区间.是否有捷径可寻?我查看了 split() 函数，但似乎需要采用数字格式才能工作，我有时间使用 POSIXct 格式.任何想法将不胜感激.

I would like to subset the data into 30 minute bins. Is there an easy way to do this? I looked at the split() function but it appears that things need to be in a numeric format for that to work, I have time in POSIXct format. Any ideas would be greatly appreciated.

推荐答案

这里有一个单行代码(dat 是你的数据框):

Here's a one-liner for you (dat being your dataframe):

split(dat, cut(strptime(paste(dat$date, dat$time), format="%F %R"),"30 mins"))

确实 cut.POSIXt 接受作为中断值

Indeed cut.POSIXt accepts as break values

间隔规范，秒"、分钟"、小时"、天"、DSTday"、周"、月"、季度"或年"之一，可选地以整数开头和一个空格，或后跟s".

an interval specification, one of "sec", "min", "hour", "day", "DSTday", "week", "month", "quarter" or "year", optionally preceded by an integer and a space, or followed by "s".

另外，我使用 %F %R 作为 %Y-%m-%d %H:%M 的快捷方式:见 ?strptime 查看所有可能的格式.

Additionnaly, I used %F %R as a shortcut for %Y-%m-%d %H:%M: see ?strptime to see all possible formats.

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