[R] Dates to numeric in for loop

[Jeff Newmiller]

"Date" means "numeric with an attribute of class='Date' ", so what actually happened was that the for loop dropped the class attribute. In most cases using the seq_along() function lets you step through index values to extract values from your original vectors. In general, any S3 object will behave this way in a for loop. 

for ( i in seq_along( dts ) ) {
  print( class( dts[ i ] ) )
}
-- 
Sent from my phone. Please excuse my brevity.

On November 14, 2017 6:15:03 AM PST, Mikkel Grum <mikkel.grum at gmail.com> wrote:
>Hi
>
>Can anyone explain why a date becomes numeric when you loop over a
>series
>of dates?
>
>> dt <- Sys.Date()
>> dt
>[1] "2017-11-14"
>> class(dt)
>[1] "Date"
>> dts <- dt - 1:0
>> class(dts)
>[1] "Date"
>>
>> for (i in dts) {
>+     print(i)
>+     print(class(i))
>+     print(as.Date(i, "1970-01-01"))
>+     print(class(as.Date(i, "1970-01-01")))
>+ }
>[1] 17483
>[1] "numeric"
>[1] "2017-11-13"
>[1] "Date"
>[1] 17484
>[1] "numeric"
>[1] "2017-11-14"
>[1] "Date"
>
>Why is this apparently not a bug? Are there other types that change
>type
>when looped over?
>
>Kind regards
>Mikkel
>
>
>
>_____________________________________________________
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