Weird issue when iterating through dates

Date has a `[.Date` method and also `[[.Date`, but it looks like a for
loop does not consider the class of the object you are iterating over,
so these are ignored and the internal representation is used.

I think this is a bug, at least in the documentation of ?"for".

Interestingly, lapply and co. do consider the class:

invisible(lapply(seq(d1, d2, by = 1), print))

works as you would expect. (The invisible() is to suppress printing
the return value.)

Gabor

On Thu, Aug 6, 2015 at 3:24 AM, Luca Cerone <luca.cerone at gmail.com> wrote:

Dear all,
I am experiencing a weird issue when iterating through dates in R
(3.1.2 and 3.2.1 on 64bit linux machines)

I am bit surprised about the behaviour of this snippet of code:

d1 <- as.Date('2015-01-01')
d2 <- as.Date('2015-01-31')

for ( dt in seq(d1,d2, by=1) ) {
  dt <- as.character(dt)
  print(dt)
}

for ( dt in as.character(seq(d1,d2, by=1)) ) {
  print(dt)
}

I can't find a good explanation why the first for loop would convert
to string the numeric interpretation
of the dates while the second one correctly (at least in my
intentions) prints the dates as string.

I am sure that it is not a bug in R but I would like to understand why
I am getting different outputs from the two for loops.

Thanks a lot in advance for your help!

Cheers,
Luca