timeDate & business day
Thanks so Michael! If you know of a tutorial or introductory document about timeDate manipulation or time series manipulation in R, can you share it? It is hard to find by googling... I'd very appreciate any advice. Young.
On Mar 12, 2007, at 9:00 PM, Michael Toews wrote:
[1] 20050104 20050105 20050106 20050107 20050110 20050111 20050113 20050114
ymd <- as.Date(as.character(ymd.int),"%Y%m%d") ymd
[1] "2005-01-04" "2005-01-05" "2005-01-06" "2005-01-07" "2005-01-10" [6] "2005-01-11" "2005-01-13" "2005-01-14"
class(ymd)
[1] "Date" While the variable ymd is actually of class Date, the format is not yyyymmdd but yyyy-mm-dd as one can see in the previous example. As Young, I do not see what I am missing here. Any hint would be appreciated. AA.
What happened in the beginning is that I had to parse the character
into a Date-Time class ("Date", in this case as you correctly
pointed out). POSIX is a kind of standard that (mainly Unix)
computers use date formatters, such as %Y for a 4-digit year, and
others. They are all listed in great detail in "?strptime" (which
means "string parse time"). In this case the input parsing format
pattern was "%Y%m%d". There were no spaces in-between each number.
When that class prints out, the default format is ISO 8601 ( see
http://en.wikipedia.org/wiki/ISO_8601 ). When R prints the class
"Date" to your screen, it decides to format it ISO 8601-style for
you. If you want to see if differently, you can try:
format(ymd,"%Y/%d/%m")
The date is actually stored internally as an ordinal, somewhat like
how MS Excel dates work. You can see how it works internally:
str(ymd)
Hopefully I've demystified some of this .. any other questions?
+mt