[R] datetime and date

[Jim Lemon]

On 02/03/2014 01:08 PM, Jim Lemon wrote:
> On 02/03/2014 12:53 PM, Yolande Tra wrote:
>> Hi,
>>
>> I have the following issue. The dataframe df has a column (Date1)
>> supposed
>> to be a date but read as a factor. There are two types of values in the
>> same column Date1
>> Type 1 are datetime like "5/23/2008 0:00:00"
>> Type 2 have no time like "1/10/13".
>>
>> When I apply the following to the date column
>> df$Date1<-as.POSIXct(as.character(df$Date1, format = "%d/%m/%Y"))
>>
>> For type 1 I got the expected result: "2008-05-23"
>> For type 2 I got NA.
>>
>> I have searched but could not solve it. Please help.
>>
> 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

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