r - How to convert decimal date format (e.g. 2011.580) to normal date format?

Question

I'm trying to change from the decimal date format (return type of cpts.ts() from the changepoint package) to the normal date format %Y-%m-%d. Example:

cpts.ts(myTimeSeries.BinSeg)
[1] 2001.667 2004.083 2008.750 2011.583 2011.917

The actual dates are sometime around August 2001, January 2004, September 2008, June/July 2011 and December 2011 (I don't know them exactly, I'm reading them off a graph).

I can't seem to find a standard method of converting this format back to the usual date format.

Can anybody help me?

Thanks

Answer 1

Slightly different results with lubridate:

library(lubridate)
decimals <- c(2001.667, 2004.083, 2008.750, 2011.583, 2011.917)

format(date_decimal(decimals), "%Y-%m-%d")
# [1] "2001-09-01" "2004-01-31" "2008-10-01" "2011-08-01" "2011-12-01"