R提取日期和时间信息 [英] R extract Date and Time Info

问题描述

我有一个看起来像这样的data.frame:

I have a data.frame that looks like this:

> df1
   Date         Name    Surname   Amount
2015-07-24      John     Smith     200

我想将日期"中的所有信息外推到新列中，所以我可以这样做:

I want to extrapolate all the infos out of the Date into new columns, so I can get to this:

> df2
   Date     Year  Month   Day    Day_w      Name    Surname   Amount
2015-07-24  2015    7     24    Friday      John     Smith     200

所以现在我想要有年，月，日和星期几.我怎样才能做到这一点?当我尝试首先使用as.Date将变量设为日期时，data.frame陷入混乱，并且Date全部变为NA(并且没有新列).感谢您的帮助！

So now I'd like to have Year, Month, Day and Day of the Week. How can I do that? When I try to first make the variable a date using as.Date the data.frame gets messed up and the Date all become NA (and no new columns). Thanks for your help!

推荐答案

也许有帮助:

df2 <- df1
dates <- strptime(as.character(df1$Date),format="%Y-%m-%d")
df2$Year <- format(dates, "%Y")
df2$Month <- format(dates, "%m")
df2$Day <- format(dates, "%d")
df2$Day_w <- format(dates, "%a")

之后，您可以根据需要重新排列df2中的列顺序.

Afterwards you can rearrange the order of columns in df2as you desire.

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