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datetime and date

6 messages · Jim Lemon, Jeff Newmiller, Yolande Tra

Jim Lemon
#
On 02/03/2014 12:53 PM, Yolande Tra wrote:
Hi Yolande,
Try this:

# first get the dates with times
df$Date1<-
  as.POSIXct(as.character(df$Date1, format = "%m/%d/%Y %H:%M:%S"))
# then fill in the ones without times
df$Date1[nchar(df$Date1) < 10]<-
  as.POSIXct(as.character(df$Date1, format = "%m/%d/%y"))

Notice that I think you got the month/day order wrong, if your first 
type is correct.

Jim
Jim Lemon
#
On 02/03/2014 01:08 PM, Jim Lemon wrote:
Hi Yolande,
Oops, major error. Change the name of the variable or you won't get the 
second lot of dates:

# first get the dates with times
df$Date2<-
  as.POSIXct(as.character(df$Date1, format = "%m/%d/%Y %H:%M:%S"))
# then fill in the ones without times
df$Date2[nchar(df$Date1) < 10]<-
  as.POSIXct(as.character(df$Date1, format = "%m/%d/%y"))

Jim
Jeff Newmiller
# 
Please read the Posting Guide, which warns you to (among other things) post in plain text and provide a reproducible example.

Read ?strptime. Note that you must provide a format that matches the data you parse with it.

If you have both formats because you are also using Excel, you can fix the inconsistent formatting quickly by re-loading it in Excel and setting a uniform cell format for that column before saving again as csv.

If you really need to do this in R, you will have to convert twice, once for each format, and transfer the non-NA values from one result vector to the other. Something like (untested): 
dtm1 <- as.POSIXct(as.character(df$Date1, format = "%d/%m/%Y %H:%M"))
dtm2 <- as.POSIXct(as.character(df$Date1, format = "%d/%m/%Y"))
ok2 <- !is.na(dtm2)
dtm1[ok2] <- dtm2[ok2]
df$Date1 <- dtm1

Note: I recommend always setting the TZ environment variable appropriately for the data you are working with before converting character to POSIXt types. Whether this works and what to set it to can be frustratingly system-dependent and since you did not follow the posting guidelines you will have to search for that info yourself.
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On February 2, 2014 5:53:22 PM PST, Yolande Tra <yolande.tra at gmail.com> wrote: