string - Consistent output of as.character for date objects in R

Question

An external R library uses the as.character function to convert objects of different classes to strings. That works fine except for my date objects (classes "POSIXlt" and "POSIXt"): Normally the output is like "2010-11-04 10:43:00" (which is perfect) but every time when time is 00:00:00 (midnight) the time component is ommited and only the date component is shown like "2010-11-04". But for further processing I need a consistent output format. So the time component should be displayed in any case.

I can't simply use the format function because the external library does the call. So I thought that overwriting the as.character function for the classes "POSIXlt" and "POSIXt" could be a solution but I don't know how. Other ideas are welcome :)

Answer 1

You can overwrite the as.character method for POSIXct objects simply by creating your own.

as.character.POSIXct <- function(x, format="%Y-%m-%d %H:%M:%S", ...)
format(x, format=format, ...)

In this case though, there is no existing as.character.POSIXct so you're not actually overwriting anything. You are, however, overriding the default as.character.POSIXt method, which is what would be called in the absence of a POSIXct method.