Convert numeric date format (YYYYMMDD; 20150101) into Year-Month

Question

Can anyone of you help in converting the date from 20150101 to abbreviated form Jan-2015 ?

I tried the below method.

x = 20150101
zoo::as.yearmon(x, "%b-%y")

But I got the below error

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

Any help would be very much appreciated.

Answer 1

There are two problems with the code in the question:

1. the input format is specified as "%b-%y" but should be "%y%m"

2. we wish to use as.yearmon.character here rather than as.yearmon.numeric so the input should be converted to "character"

Therefore, try this:

 library(zoo)
 ym <- as.yearmon(as.character(20150101), "%Y%m")

giving:

> ym
[1] "Jan 2015"

Note that "yearmon" objects are internally stored as year + fraction where fraction is 0 for Jan, 1/12 for Feb, ..., 11/12 for Dec. Externally they are rendered as an abbreviated month followed by a space and the year as shown.

The above may be sufficient but if not to convert it to a character string with format "%b-%y" or "%b-%Y" use format :

format(ym, "%b-%y")
## [1] "Jan-15"

format(ym, "%b-%Y")
## [1] "Jan-2015"

Answer 2

You can use a combination of strptime to convert the string to a date object and format to format to what you want:

date = "20150101"
format(strptime(date,format="%Y%m%d"),"%b-%Y")

Answer 3

Using lubridate and zoo packages:

library(lubridate)
library(zoo)

x <- "20150101"

as.yearmon(as.Date(ymd(x)))

[1] "jan 2015"