Converting Date formats in R [closed] - r

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dates <- as.Date(dli$Dates)
class(dates)
[1] "Date"
dates
[1] "2016-01-01" "2016-01-02" "2016-01-03" "2016-01-04" "2016-01-05" "2016-01-06"
[7] "2016-01-07" "2016-01-08" "2016-01-09" "2016-01-10" "2016-01-11" "2016-01-12"
[13] "2016-01-13" "2016-01-14" "2016-01-15" "2016-01-16" "2016-01-17" "2016-01-18"
[19] "2016-01-19" "2016-01-20" "2016-01-21" "2016-01-22" "2016-01-23" "2016-01-24"
[25] "2016-01-25" "2016-01-26" "2016-01-27" "2016-01-28" "2016-01-29" "2016-01-30"
[31] "2016-01-31" "2016-02-01" "2016-02-02" "2016-02-03" "2016-02-04" "2016-02-05"
[37] "2016-02-06" "2016-02-07" "2016-02-08" "2016-02-09" "2016-02-10" "2016-02-11"
This is my date format , so i need to convert it into "2016-month-day"
I am getting NA values
dates <- as.Date(dli$Dates,"%d/%b/%Y")
class(dates)
[1] "Date"
dates
[1] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
[31] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
[61] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
[91] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
[121] NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA NA
can you give any suggestions
Thanks in Advance

Answer 1

Good practice is to store date in R as YYYY-MM-DD, and your strings already seem to be at the good format, but :
The format you're passing to as.Date must describe what the strings contain, not what you're expecting as an output.
"%d/%b/%Y" stands for "day as a number (0-31) slash abbreviated month slash 4-digit year", and your strings format are "4-digit year - month as a number - day as a number".
If you want to format the date, you need to call format :
> date <- "2016-01-01"
> date <- as.Date(date, format = "%Y-%m-%d")
> date
[1] "2016-01-01"
> format(date, "%d/%b/%Y")
[1] "01/jan/2016"

Answer 2

To obtain your required format i.e., 2016-month-day , you can use format function once you have converted vector of strings to Date type.
I hope below code snippet clears your doubt.
> d = c("2016-02-08","2016-02-18","2015-02-08","2016-02-02")
> class(d)
[1] "character"
> d = as.Date(d)
> class(d)
[1] "Date"
> d = format(d,"%Y-%b-%d")
> d
[1] "2016-Feb-08" "2016-Feb-18" "2015-Feb-08" "2016-Feb-02"
Format function converts the date type objects into the required format. Refer to this link for more information on date type formatting.

Answer 3

If you just want to render your dates in this format, then use format:
x <- as.Date("2016-01-01")
format(x, "%Y %b %a %d")
[1] "2016 Jan Fri 01"
There is a separation of concerns here. If you already have your date information stored in R as date types, then you need not change anything internally to extract further information from those dates.
Demo

Answer 4

You would use as.Date() to convert between dates saved as character and Date objects.
If you want to change the format of a Date object, you can use format().
You have specified "2016-month-day" as the desired format of the dates in the question, but in the code you provide you are using "%d/%b/%Y". The way this works is: the % indicates that the next character will be a conversion specification, everything else (e.g. (- or /) will be used for finding / adding delimiter to the date representation. (see ?strptime for details).
So in your case, just use
dates <- format(dli$Dates, format = "%Y-%b-%d")
to get the result specified in the text of the question:
[1] "2016-Jan-01" "2016-Jan-02" "2016-Jan-03" "2016-Jan-04" "2016-Jan-05"
or this:
dates <- format(dli$Dates, format = "%Y/%b/%d")
to get what you have used in the code snipped:
[1] "2016/Jan/01" "2016/Jan/02" "2016/Jan/03" "2016/Jan/04" "2016/Jan/05"

Answer 5

You can use the package lubridate to convert to a date with ymd then format it for the way you want it displayed
Dates_df <- mutate(Dates, dli = format(ymd(dli), "%Y/%b/%d")
(I use dplyr here, I assume you have other variables in Dates)
without dplyr if you just want to keep the dates in a vector:
Dates_vec <- format(ymd(Dates$dli), "%Y/%b/%d")