R devel - May 2002 - I() fails on objects of class POSIXct (PR#1587)

Although the documentation is somewhat sketchy, I() can be used to create
objects of class AsIs:
> I("a")
[1] "a"
attr(,"class")
[1] "AsIs"      "character"
> I(4)
[1] 4
attr(,"class")
[1] "AsIs"    "numeric"
> I(4 + 0i)
[1] 4+0i
attr(,"class")
[1] "AsIs"    "complex"
> 
This fails for objects of class POSIXct.
> class(ISOdate(2002, 5, 21))
[1] "POSIXt"  "POSIXct"
> I(ISOdate(2002, 5, 21))
Error in names(x) : evaluation is nested too deeply: infinite
recursion?
>
Interestingly enough, it produces an (incorrect?) answer for objects of class
POSIXlt
> class(as.POSIXlt(ISOdate(2002, 5, 21)))
[1] "POSIXt"  "POSIXlt"
> I(as.POSIXlt(ISOdate(2002, 5, 21)))
[1] "  0" "  0" "  8" " 21" " 
4" "102" "  2" "140" " 
1"
> 
Of course, this may not be a bug since it is not clear that I() is documented
to do anything like this.
> R.version
         _                   
platform sparc-sun-solaris2.6
arch     sparc               
os       solaris2.6          
system   sparc, solaris2.6   
status                       
major    1                   
minor    5.0                 
year     2002                
month    04                  
day      29                  
language R                   

Regards,

David Kane

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a296180@mica.fmr.com writes:
> Although the documentation is somewhat sketchy, I() can be used to create
> objects of class AsIs:
...
> This fails for objects of class POSIXct.
> 
> > class(ISOdate(2002, 5, 21))
> [1] "POSIXt"  "POSIXct"
> > I(ISOdate(2002, 5, 21))
> Error in names(x) : evaluation is nested too deeply: infinite recursion?
> >
Actually I() works fine, but the resulting object has a print
method problem:
>  x <- I(ISOdate(2002, 5, 21))
> x
Error in names(x) : evaluation is nested too deeply: infinite
recursion?
> dput(x)
structure(1021982400, class = c("AsIs", "POSIXt",
"POSIXct"))

Looks like the issue is that print calls format.AsIs which calls toString
which calls paste which calls as.character which calls format which....

----
> Interestingly enough, it produces an (incorrect?) answer for objects of
class
> POSIXlt
> 
> > class(as.POSIXlt(ISOdate(2002, 5, 21)))
> [1] "POSIXt"  "POSIXlt"
> > I(as.POSIXlt(ISOdate(2002, 5, 21)))
> [1] "  0" "  0" "  8" " 21" " 
4" "102" "  2" "140" "  1"
> > 
However, that is not particularly incorrect:
> dput(as.POSIXlt(ISOdate(2002, 5, 21)))
structure(list(sec = 0, min = 0, hour = 14, mday = 21, mon = 4, 
    year = 102, wday = 2, yday = 140, isdst = 1), .Names = c("sec", 
"min", "hour", "mday", "mon",
"year", "wday", "yday", "isdst"
), class = c("POSIXt", "POSIXlt"), tzone = c("",
"CET", "CEST"
))

(Notice the 6hr time diff..)

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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