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

[Jacques VESLOT]

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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