将UNIX时间戳列转换为R中的星期几

问题描述：

我正在使用 R 中标有"mydata"的数据框.第一列标记为"ts"，其中包含unix时间戳字段.我想将这些字段转换为一周中的几天.

I am working with a data frame in R labeled "mydata". The first column, labled "ts" contains unix timestamp fields. I'd like to convert these fields to days of the week.

我尝试使用strptime和POSIXct函数，但不确定如何正确执行它们:

I've tried using strptime and POSIXct functions but I'm not sure how to execute them properly:

> strptime(ts, "%w")

-返回此错误:

"as.character(x)中的错误:无法将类型'closure'强制转换为类型为'character'的向量"

"Error in as.character(x) : cannot coerce type 'closure' to vector of type 'character'"

我也尝试过使用POSIXct将其转换为人类可读的格式:

I also just tried just converting it to human-readable format with POSIXct:

as.Date(as.POSIXct(ts, origin="1970-01-01"))

-返回此错误:

"as.POSIXct.default(ts，origin ="1970-01-01")中的错误:不知道如何将"ts"转换为"POSIXct"类"

"Error in as.POSIXct.default(ts, origin = "1970-01-01") : do not know how to convert 'ts' to class "POSIXct""

更新:以下是对我有用的东西:

Update: Here is what ended up working for me:

> mydata$ts <- as.Date(mydata$ts)

然后

> mydata$ts <- strftime( mydata$ts , "%w" )

答

当 POSIXlt 直接为您提供此功能且 strftime 调用 as.POSIXlt .

No need to go all the way to strftime when POSIXlt gives you this directly, and strftime calls as.POSIXlt.

wday <- function(x) as.POSIXlt(x)$wday

wday(Sys.time()) # Today is Sunday
## [1] 0

如果想要字符而不是数字输出，还可以使用 weekdays 函数:

There is also the weekdays function, if you want character rather than numeric output:

weekdays(Sys.time())
## [1] "Sunday"

将UNIX时间戳列转换为R中的星期几

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