dplyr-mutate_each-对POSIXlt的逐级强制转换失败 [英] dplyr - mutate_each - colswise coercion to POSIXlt fails

问题描述

我最近遇到了dplyr，并且-作为新手-非常喜欢。因此，我尝试将一些base-R代码转换为dplyr代码。

I recently came across dplyr and - as a newbie - like it very much. Hence, I try to convert some of my base-R code into dplyr-code.

在处理空中交通管制数据时，我正在使用lubridate和as.POSIXlt强制解析时间戳以解析嵌入在mutate_each（）调用中的时间戳。我需要POSIXlt格式，因为以后必须处理本地时间（在不同位置）。
读入数据会得到一个字符数据框。下面是一个简单的示例：

Working with air traffic control data, I am struggling with coercing timestamps using lubridate and as.POSIXlt to parse timestamps embedded in a mutate_each() call. I need the POSIXlt format as I have to work with local times (at different locations) later on. Reading in the data delivers a data frame of characters. The following is a simplistic example:

ICAO_ADEP <- c("DGAA","ZSPD","UAAA","RJTT","KJFK","WSSS")
MVT_TIME_UTC <- c("01-Jan-2013 04:02:24", NA,"01-Jan-2013 04:08:18", NA,"01-Jan-2013 04:17:11","01-Jan-2013 04:21:52")
flights <- data.frame(ICAO_ADEP, MVT_TIME_UTC)

我写的函数如下：

make_POSIXlt <- function(vec, tz="UTC"){
vec <- parse_date_time(vec, orders="dmy_hms", tz=tz)
vec <- as.POSIXlt(vec, tz=tz)
}

使用单个列：

flights$MVT_TIME_UTC <- make_POSIXlt(flights$MVT_TIME_UTC)

如果我运行以下dplyr代码，该函数将失败：

If I run the following dplyr code the function fails:

flights$BLOCK_TIME_UTC <- mutate_each(flights, funs(make_POSIXlt(.)), MVT_TIME_UTC)
Error: wrong result size (9), expected 6 or 1

该问题应与as.POSIXlt调用相关联。如果此行被注释掉，代码将在mutate_each中工作，并将时间戳强制为POSIXct。

The issue should be linked with the as.POSIXlt call. If this line is commented out the code works within mutate_each and coerces the timestamp into POSIXct.

关于什么地方有问题的任何想法/帮助？
显然，我的数据有几个时间戳，我想使用mutate_each（或任何其他合适的dplyr函数）强制使用...

Any idea/help on what is wrong? Obviously, my data has several timestamps that I would like to coerce with mutate_each (or any other suitable dplyr function) ...

推荐答案

大约4年后，我再次提出问题，但我意识到我忘记将其标记为已回答。但是，这也使我有机会记录下（相对）简单的类型强制如何（同时）使用 dplyr 和 lubridate 。

Revisiting my question about 4 years later, I realised that I forgot to mark it as answered. However, this also gives me the chance to document how this (relatively) simple type coercion can (meanwhile) elegantly solved with dplyr and lubridate.

主要经验教训：

1. 从不使用带有数据框的POSIXlt（及其后继兄弟，
   ，尽管您现在可以使用列表列了）。


2. 使用 lubridate 包中的有用解析器功能强制日期时间戳记。

1. never use POSIXlt with a data frame (and its later brother tibble, although you can now work with list columns).
2. coerce date-timestamps with the helpful parser functions from the lubridate package.

例如上述示例

ICAO_ADEP <- c("DGAA","ZSPD","UAAA","RJTT","KJFK","WSSS")
MVT_TIME_UTC <- c("01-Jan-2013 04:02:24", NA,"01-Jan-2013 04:08:18", NA,"01-Jan-2013   04:17:11","01-Jan-2013 04:21:52")
flights <- data.frame(ICAO_ADEP, MVT_TIME_UTC)

flights <- flights %>% mutate(MVT_TIME_UTC = lubridate::dmy_hms(MVT_TIME_UTC)

将强制使用MVT_TIME_UTC中的时间戳。请查阅lubridate上的文档以获取其他解析器和/或如何处理本地时区。

will coerce the timestamps in MVT_TIME_UTC. Check the documentation on lubridate for other parsers and/or how to handle local time zones.

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