Julian dates

I guess there's a "bug" in chron as you cannot pass the argument cut.off to year.expand. Adding ,... in chron arguments and along the code ,... to convert.dates does the trick.

HIH,

Stefano

Hi all,
I have problems with years of dates using "chron" package.
I don't understand why R by this istruction:

dates("01/02/29",out.format="d/m/year")

[1] 02/Jan/2029

dates("01/02/30",out.format="d/m/year")

[1] 02/Jan/1930

reads "29" as 2029
and "30" as 1930. How could I change to read "00" to "05" like 2000 to 2005 and "06" to "99" like 1906 to 1999 ?
Thank you
 
Massimiliano

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Hi all,
I have problems with years of dates using "chron" package.
I don't understand why R by this istruction:

dates("01/02/29",out.format="d/m/year")

[1] 02/Jan/2029

dates("01/02/30",out.format="d/m/year")

[1] 02/Jan/1930

reads "29" as 2029
and "30" as 1930. How could I change to read "00" to "05" like 2000 to
2005 and "06" to "99" like 1906 to 1999 ?

I'm puzzled by the above:

dates("01/02/29",out.format="d/m/year")

[1] 02/Jan/2029

dates("01/02/30",out.format="d/m/year")

[1] 02/Jan/1930

so chron apparently acts as though time began at 01/01/1930.

However:

?chron

-->
 origin.: a vector specifying the date with respect to which Julian
          dates are computed.  Default is 'c(month = 1, day = 1,
          year = 1970)'

(which is the orthodox origin of time according to Unix) and, indeed,

origin(dates("01/02/29",out.format="d/m/year"))

month   day  year 
    1     1  1970 

So why does Massimiliano's example behave as though the origin
were 01/01/1930?

Best wishes,
Ted.


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origin(dates("01/02/29",out.format="d/m/year"))

month   day  year 
    1     1  1970 

So why does Massimiliano's example behave as though the origin
were 01/01/1930?

It doesn't.  It behaves as if he wrote "01/02/2029" and he intended
"01/02/1929" (but chron failed to read his mind).  That is an undocumented
`feature' of the auxiliary function year.expand(), whose use is an
undocumented `feature' of convert.dates() (whose use is ..., well it gets
boring).

You will find all date-conversion routines do something like this with 
incompletely specified years.  Read the help on %y in ?strptime.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595