Why does iterating through a Date
or POSIXct
object result in numeric
? For example:
test = as.Date("2009-01-01")
print( class( test ) )
# [1] "Date"
for ( day in test )
{
print( class( day ) )
}
# [1] "numeric"
The same thing happens with POSIXct
:
test = as.POSIXct("2009-01-01")
print( class( test ) )
# [1] "POSIXct" "POSIXt"
for ( day in test )
{
print( class( day ) )
}
# [1] "numeric"
?"for"
says that seq
(the part after in
) is "[A]n expression evaluating to a vector (including a list and an expression) or to a pairlist or 'NULL'".
So your Date
vector is being coerced to numeric
because Date
objects aren't strictly vectors:
is.vector(Sys.Date())
# [1] FALSE
is.vector(as.numeric(Sys.Date()))
# [1] TRUE
The same is true for POSIXct
vectors:
is.vector(Sys.time())
# [1] FALSE
is.vector(as.numeric(Sys.time()))
# [1] TRUE