问题
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?
回答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"
来源：https://stackoverflow.com/questions/13859905/returning-a-vector-of-class-posixct-with-vapply