How to make an empty vector of POSIXct

Question

I want to make an empty vector of POSIXct so that I can put a POSIXct in it:

vec <- vector(\"POSIXct\", 10)
vec
vec[1] <- \"2014-         


        

Answer 1

I would go for Gregor's solution. I first went with Rich Scriven's solution but then got an error when I tried to compute the difference for a Non-NA element later as shown in the example below

t1 <- as.POSIXct("2014-10-27 18:11:36 PDT")
t2 <- as.POSIXct("2014-11-20 18:11:36 PDT")
x <- .POSIXct(character(10))
x[1] <- t1

difftime(t2, t1)
#R Time difference of 24 days

# fails
difftime(t2, x[1])
#R Error in unclass(time1) - unclass(time2) : 
#R   non-numeric argument to binary operator

unclass(x[1]) # character
#R [1] "1414429896"
unclass(t1)
#R [1] 1414429896
#R attr(,"tzone")
#R [1] ""

x <- .POSIXct(rep(NA_real_, 10))
x[1] <- t1
difftime(t2, x[1]) # all good
#R Time difference of 24 days

This can even lead to strange bugs like this one which can take a while to discover

t1 <- as.POSIXct("2001-07-24 CEST")
t2 <- as.POSIXct("2002-08-29 CEST")
x <- .POSIXct(character(10))
x[1] <- t1

t2 < t1
#R [1] FALSE
t2 < x[1] # oh boy 
#R [1] TRUE

# the reason (I think)
unclass(t2)
#R [1] 1030572000
#R attr(,"tzone")
#R [1] ""
unclass(x[1])
#R [1] "995925600"

"995925600" > 1030572000
#R [1] TRUE