R help - Mar 2007 - timeDate & business day

I have a daily time series and have two questions to get some help with.

Firs,t I have dates in simple numeric values. e.g.
ymd
[1] 20050104 20050105 20050106 20050107 20050110 20050111 20050113 20050114
 [9] 20050118 20050120 20050121 20050124 20050125 20050126 20050127 20050128
[17] 20050201 20050202 20050203 20050204
Now, I'd like to compute statistics, e.g. acf, by business days. So, I try
to convert it into timeDate class. But, when I try to change date format,
this is what I am getting:
> tt =
timeDate('20050101',format=c('%Y%m%d'),FinCenter='GMT')
> unclass(tt)
list()
attr(,"Data")
[1] "2005-01-01"
attr(,"Dim")
[1] 1
attr(,"format")
[1] "%Y-%m-%d"
attr(,"FinCenter")
[1] "GMT"
Somehow, I can't change the format to 'yyyymmdd' (e.g. 19950401)

Also, I was wondering if there is a function similar to 'timeRelative'
in Splus. So that actually I can add or substract n business days to and
from timeDate.

Or, is there a simpler way to compute statistics for daily time series?
( based on business days )

Thanks a lot

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Those numbers look like ... well, numbers. You want characters! Try 
converting the integer to a character before trying to do a string 
parse, e.g.:

ymd.int <- c(20050104, 20050105, 20050106, 20050107, 20050110, 20050111, 
20050113, 20050114)
ymd <- as.Date(as.character(ymd.int),"%Y%m%d")

As far as the other functions you are looking at ("timeDate", 
"timeRelative") -- I've never seen these, so I'm guessing they
are
S-PLUS. In R, you can use "diff" or "difftime" (which works
with "Date"
and "POSIXlt"-or Date-Time classes) , e.g.:

diff(ymd)
diff(ymd,2)
diff(ymd,3)

or do some arithmetic:

difftime(ymd[1],ymd[4])
difftime(ymd[1],ymd[4],unit="weeks")

Hopefully this is helpful to you!
+mt