On Apr 22, 2012, at 2:18 PM, Raghuraman Ramachandran wrote:
I also tried:
test$Date=as.POSIXct(test$Date,format="%m%d%y")
Well, as became apparent when you eventually offered an example, you
have dates in dd/mm/yyyy format, so it's hardly surprising that "it
didn't work" with a format that didn't match your data.
?strptime
?as.Date
test=cbind(test,day.of.week=format(test$Date,format="%A"))
head(test)
Date Open High Low Close Volume Adj.Close day.of.week
1 <NA> 2.33 2.34 2.31 2.31 5366000 2.31 <NA>
2 <NA> 2.35 2.36 2.33 2.35 5382000 2.35 <NA>
3 <NA> 2.35 2.38 2.34 2.36 9606000 2.36 <NA>
4 <NA> 2.34 2.34 2.30 2.33 9596000 2.33 <NA>
5 <NA> 2.32 2.35 2.31 2.31 5941000 2.31 <NA>
6 <NA> 2.34 2.36 2.32 2.32 10332000 2.32
It didnt help.
Thx
Raghu
On Sun, Apr 22, 2012 at 6:41 PM, Jeff Newmiller <jdnew...@dcn.davis.ca.us
>wrote:
On Sun, 22 Apr 2012, Hasan Diwan wrote:
Raghu,
On 22 April 2012 09:53, Raghuraman Ramachandran <optionsra...@gmail.com
wrote:
I have a data frame (from CSV file) which has its first column
called
Date.
The Date is in the format mm/dd/yyyy. I was trying to get the
weekday for
these dates and I tried using wday() and day.of.week() functions
and both
of them gave me precisely the wrong answers. I think the issue
lies in
the
proper formatting of dates. The class of this column is a factor
class
and
hence I tried converting into POSIXlt, xts, zoo objects and yet I
could
not
get the weekday correctly. Anyone has any suggestions please?
Try this:
# assume dataIn is where the CSV files data is...
dataIn$Date <- as.POSIXct(dataIn$Date, format='%m/%d/%y')
By far the most common error I see is failing to import the Date
column as
character, instead allowing the import function to convert it to
factor,
after which computations (such as the above suggestion) use the
hidden
factor index instead of the visible character representation, which
further
mystifies beginners. The conversion above will only work correctly
if the
column was imported as character. E.g.
dataIn <- read.csv( file="yourdatafile", as.is=TRUE )
OP: Use the str() function to see what types you are working with,
and in
future R-help queries send dput() of the data and code you have
tried if we
are to be able to reproduce your attempts effectively rather than
reading
your mind.
dataIn <- cbind(dataIn, day.of.week = format(dataIn$Date,
format='%A')
Why not just
dataIn$day.of.week <- weekdays( dataIn$Date )
?
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