Re: [R] Converting strings to date

Roger D. Peng Tue, 09 Nov 2004 05:55:39 -0800

You need to be more specific when you say "it works" =) strptime() returns a POSIXlt object whose printed representation appears to be a string (but it is a list). What you want, I think, is either as.POSIXct() or as.Date(). See ?DateTimeClasses.

-roger

Jo�o Mendes Moreira wrote:

Hello,

I have the following problem:
test is a data frame with 9 fields. The field test$Date is factorized with 
dates. The format is dd-mm-yyyy (using Oracle notation). I want to convert this 
to Date in '%Y-%m-%d format.
What I am doing is:
for (i in 1:nrow(test))
  {
   test[i,]$Data<-strptime(substring(test[i,]$Data,1,10),"%d-%m-%Y")
  }

test is a data frame.

The error is: Error in "$<-.data.frame"(`*tmp*`, "Data", value = list(sec = 0, min = 0, : replacement has 9 rows, data has 1

But if I do:
strptime(substring(test[1:nrow(teste),]$Data,1,10),"%d-%m-%Y")
it works! Why the assignement does not work?

Thanks

Joao Moreira
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--
Roger D. Peng
http://www.biostat.jhsph.edu/~rpeng/

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