[R] Applying strptime() to a data set or array

[Jacques VESLOT]

it's probably a factor, not a string vector...
so i would do as.vector or as.character - but it may be not necessary !
 
as.POSIXct(strptime(as.vector(A$date),...))

or:
seq( from = ISOdate(2006,02,28, 12, 0, 0, tz=""),
     to = ISOdate(...), by="30 min")


Andrew Athan a écrit :

>
> A$date is already a string, as read from the file.  I tried it anyway, 
> for you...
>
> > A$date<-strptime(as.character(A$date),"%Y-%m-%d %H:%M:%s")
> Error in "$<-.data.frame"(`*tmp*`, "date", value = list(sec = c(0, 0,  :
>        replacement has 9 rows, data has 3198
> >
>
> A.
>
> Jacques VESLOT wrote:
>
>> maybe you need to transform A$date to character:
>> A$date <- strptime(as.character(A$date), ...)
>>
>> see also:
>> ?ISOdatetime
>>
>> Andrew Athan a écrit :
>>
>>> I'm sure this is just the result of a basic misunderstanding of the 
>>> syntax of R, but I am stumped.
>>>
>>> A <- 
>>> read.table(file="sumByThirtyMinute.csv",sep=",",col.names=c("date","pandl")) 
>>>
>>>
>>> A now consists of thousands of rows, but A$date is a string...
>>> ...
>>> 3183 2006-02-28 12:00:00    548.470
>>> 3184 2006-02-28 12:30:00    515.240
>>> 3185 2006-02-28 13:00:00    140.120
>>> 3186 2006-02-28 13:30:00    450.940
>>> 3187 2006-02-28 14:00:00    318.570
>>> ...
>>>
>>>
>>>
>>>
>>> So, I try to convert A$date to a POSIXlt ...
>>>
>>> A[,1]<-strptime(A$date,"%Y-%m-%d %H:%M:%s")
>>> A$date<-strptime(A$date,"%Y-%m-%d %H:%M:%s")
>>>
>>>
>>> which gives me a warning that the length of the array I am trying to 
>>> replace A$date with is 9 ... but if I print 
>>> strptime(A$date,"%Y-%m-%d %H:%M:%s"), it clearly has thousands of 
>>> rows.  Yet, if I ask for length(strptime(A$date,"%Y-%m-%d 
>>> %H:%M:%s")), I get 9.
>>>
>>> What am I doing wrong?  Do I need to convert the return value of 
>>> strptime(A$date,"%Y-%m-%d %H:%M:%s") to some array/vector/matrix 
>>> datatype before attempting to assign it?
>>>
>>> Thanks,
>>> Andrew
>>>
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>>>  
>>>
>>
>