I also tried:

> test$Date=as.POSIXct(test$Date,format="%m%d%y")
> 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 <jdnewmil@dcn.davis.ca.us>wrote:

> On Sun, 22 Apr 2012, Hasan Diwan wrote:
>
> Raghu,
>>
>> On 22 April 2012 09:53, Raghuraman Ramachandran <optionsraghu@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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