Question

I have list of dates having POSIXct class as follows (just a minimum working example):

L <- list(as.POSIXct("2012-12-12 12:12:12"), as.POSIXct("2012-12-12 12:12:12"))

I need to retrieve a vector of class POSIXct from it. This rules out lapply, and leaves me with sapply and vapply. I apply them as follows:

sapply(L, "[[", 1)

and this returns:

[1] 1355310732 1355310732

Converting this vector to POSIXct gives error as origin must be provided. I also tried vapply:

vapply(L, "[[", as.POSIXct(Sys.time()), 1)

but also get numeric vector returned:

[1] 1355310732 1355310732

Also unlist does not produce the desired POSIXct vector:

> unlist(L)
[1] 1355310732 1355310732 

In short, how do I extract a list of POSIXct values into a POSIXct vector?

Answer 1

What about do.call?

L <- list(as.POSIXct("2012-12-12 12:12:12"), as.POSIXct("2012-12-12 12:12:12"))
do.call(c, L) # Execute function c on a list L of arguments.
[1] "2012-12-12 12:12:12 CET" "2012-12-12 12:12:12 CET"