[R] CSV file and date. Dates are read as factors!

[roger bos]

Working with dates is not easy (for me at least).  I always manage to
get it done, but the code is somewhat messy.  I have not tried using
the Hmisc package as Frank suggested, but I will show you my code as
an alternate way:

w <- unclass((as.Date(as.character(dataMat$fy1_period_end_date),
format="%m/%d/%Y") - as.Date(datec[i], format="%m/%d/%Y"))/365)

w is the time (in days) between two dates.  You can see that I had to
"unclasss" the first date vector.  I read my files in csv also, so I
am sure something similar can be made to work for you.

HTH,

Roger




On 7/27/05, John Sorkin <jsorkin at grecc.umaryland.edu> wrote:
> I am using read.csv to read a CSV file (produced by saving an Excel file
> as a CSV file). The columns containing dates are being read as factors.
> Because of this, I can not compute follow-up time, i.e.
> Followup<-postDate-preDate. I would appreciate any suggestion that would
> help me read the dates as dates and thus allow me to calculate follow-up
> time.
> Thanks
> John
> 
> John Sorkin M.D., Ph.D.
> Chief, Biostatistics and Informatics
> Baltimore VA Medical Center GRECC and
> University of Maryland School of Medicine Claude Pepper OAIC
> 
> University of Maryland School of Medicine
> Division of Gerontology
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
> 
> 410-605-7119
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> jsorkin at grecc.umaryland.edu
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