splitting date and time in data frame

问题:

I have a column list of dates in data frame with date format 201001011200 as %Y%m%d%H%M. I wanted to split them as %Y%m%d and %H%M as Date and Time.

I tried to as.Date(data$Date,origin = "1970-01-01") but I got an error message

Error in charToDate(x) : character string is not in a standard unambiguous format

The class of the date is numeric. So I tried to convert it to characterand applied the above as.Date function but was not helpful.

Any idea? Thank you in advance.

EDIT

Here is a sample of my data:

Index Date          rank amount
81211 201004090000  11 4.9
81212 201004090100  11 4.6
81213 201004090200  11 3.3
81214 201004090300  11 2.7
81215 201004090400  11 3.1
81216 201004090500  11 3.7
81217 201004090600  11 4.0
81218 201004090700  11 4.2
81219 201004090800  11 4.2
81220 201004090900  11 4.0

回答1:

Updated Answer: Beginning with your example data, you can do

data$Date <- as.POSIXct(as.character(data$Date), format =  "%Y%m%d%H%M")

to change the column to a POSIX datetime value. Then, to extract the date and time into two separate columns, you can do

data$date <- as.character(as.Date(data$Date))
data$time <- format(data$Date, "%T")

This gives the following updated data frame data

   Index                Date rank amount       date     time
1  81211 2010-04-09 00:00:00   11    4.9 2010-04-09 00:00:00
2  81212 2010-04-09 01:00:00   11    4.6 2010-04-09 01:00:00
3  81213 2010-04-09 02:00:00   11    3.3 2010-04-09 02:00:00
4  81214 2010-04-09 03:00:00   11    2.7 2010-04-09 03:00:00
5  81215 2010-04-09 04:00:00   11    3.1 2010-04-09 04:00:00
6  81216 2010-04-09 05:00:00   11    3.7 2010-04-09 05:00:00
7  81217 2010-04-09 06:00:00   11    4.0 2010-04-09 06:00:00
8  81218 2010-04-09 07:00:00   11    4.2 2010-04-09 07:00:00
9  81219 2010-04-09 08:00:00   11    4.2 2010-04-09 08:00:00
10 81220 2010-04-09 09:00:00   11    4.0 2010-04-09 09:00:00

---

Original Answer: If you are starting with a numeric value, wrap it in as.character() then run it through as.POSIXct() to get a POSIX date-time value.

data$Date <- as.POSIXct(as.character(data$Date), format = "%Y%m%d%H%M")

As an example I will use 201001011200 as you gave.

(x <- as.POSIXct(as.character(201001011200), format = "%Y%m%d%H%M"))
# [1] "2010-01-01 12:00:00 PST"

Then to separate out the date and time you can do the following.

list(as.Date(x), format(x, "%T"))
# [[1]]
# [1] "2010-01-01"
# 
# [[2]]
# [1] "12:00:00"

That gives Date and character classed items, respectively. For a plain old character vector, just use format() twice.

c(format(x, "%m-%d-%Y"), format(x, "%T"))
# [1] "01-01-2010" "12:00:00"  

or

c(as.character(as.Date(x)), format(x, "%T"))
# [1] "2010-01-01" "12:00:00"