Gabor,
Thanks much. Your solution is elegant. My overall scheme is to take
present date, and check whether it is a weekend, if not, then create a
string based on the date, to concatenate into a url link for
download.file( ). The files I need to download have a part which is in
the format: mmddyy. I am working to make myself a system to connect to
exchanges, and download end of day files from their servers. Knowing
that there won't be any files for weekends, I want to omit making
those requests (later I'd add something to skip a list of given
exchange holidays).
So I am making this string from the date, if it isn't a weekend,
concatenating to make the URL, downloading the file, unzipping it and
decrementing the date by a day to repeat the test for weekday and
following action. If to begin with the date is of a weekend, then
'else' should take over and decrement the date. I also have problem
My crude solution is this (I am just 4-day old into learning/using R):
#begin script
date <- as.POSIXlt(Sys.time()) #present date
for (i in 1:difftime(as.POSIXlt(Sys.Date()),"2007-10-01"))
if (date$wday != 0 & date$wday != 6) #check whether
weekday
{
datestr <- as.character(date, "%d%m%y") #make date
character string ddmmyy
url <-
paste("http://www.bseindia.com/bhavcopy/eq",datestr,"_csv.zip",sep="";)
file <- paste("C:\\Program
Files\\R\\R-2.5.0\\data"\",datestr,"_csv.zip",sep="")
download.file(url, destfile = file, mode = "wb")
zip.unpack(file, cat("C:\\Program Files\\R\\R-2.5.0\\data\\"))
date <- date - 86400
}
else (date <- date-86400)
#end script
The above URLs would point to Bombay Stock Exchange's data files (if
the script works). Thanks again. The code you already suggested would
help me make the date sequence, but I am not sure how I could extract
the mmddyy string from it. Also, I might end up making a list for
dates extending to about 10 years in the past (~2600 working days), so
I was more keen on not creating one long list.
Vishal Belsare
On 10/15/07, Gabor Grothendieck <[EMAIL PROTECTED]> wrote:
> See ?seq.Date, e.g.
>
> now <- Sys.Date()
> dd <- seq(now - 20, now, by = "day")
> dd[as.POSIXlt(dd)$wday %% 6 != 0]
>
> and have a look at R News 4/1.
>
> On 10/15/07, Vishal Belsare <[EMAIL PROTECTED]> wrote:
> > date <- as.POSIXlt(Sys.time()) #present date
> > for (i in 1:difftime(as.POSIXlt(Sys.Date()),"2007-10-01"))
> > if (date$wday != 0 & date$wday != 6) {print(date);assign("date",
> > (date-86400))} else (assign("date", (date-86400)))
> >
> >
> > I am trying to print dates from present day to a day in the past, but
> > omitting weekends. I am not doing something right, but can't figure
> > out what. Help appreciated!
> >
> >
> > Vishal Belsare
> >
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