[R] Problems Dating....

[Marc Schwartz]

On Jun 1, 2011, at 3:59 PM, Struckmeier, Nathanael wrote:

> I'm trying to convert a column in a data frame with dates from a
> "Factor" type to a "Date Object" but I am encountering and error. (I am
> having trouble plotting an x,y scatter and I suspect it's something with
> my data format). I have a table with two columns and 8,000 rows. 
> 
>> dsort=read.delim("C:\\Documents and Settings\\E066582\\My
> Documents\\R\\R-2.13.0\\bin\\dsort.txt")
> 
> 
> 
> "dsort"                                                #name of
> data.frame
> 
>> colnames(dsort)[1]                     #name of column 1
> 
> [1] "Date"
> 
>> colnames(dsort)[2]                     #name of column 2
> 
> [1] "Qty"
> 
>> class(dsort$Date)                         #checked data type of column
> "Date" and it came back as a factor
> 
> [1] "factor"
> 
>> Date2=as.Date(dsort$Date)    #attempt at changing the data type from a
> factor to a date object (see error below).
> 
> Error in charToDate(x) : 
> 
>  character string is not in a standard unambiguous format
> 
> 
> 
> Dates in my table are listed in "3/4/2007" format. 
> 
> StatBat2


After seeing your subject line and your e-mail address, I was going to suggest a dozen roses and some Moose Munch...  ;-)

When you convert a character/factor to a Date, you need to specify the format of the object to be converted:

> as.Date("3/4/2007", format = "%m/%d/%Y")
[1] "2007-03-04"

See ?as.Date and ?strptime for more information and format specifications.

HTH,

Marc Schwartz