Converting strings to date

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You want as.Date, not strptime that gives you a *list*.

Please do read the help pages before posting, as the the posting guide
asks you to.

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?

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595
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
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
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