how to read only time in a data frame

Question

I have a data frame of date, time. I read it with as.POSIXct, but i don't need the dates, i only need the time. then i want to make box plot with the times that i have. how i can only read the time data?

C1
   13/07/2017 15:15
   13/07/2017 15:02
   13/07/2017 14:40
   13/07/2017 15:15
   13/07/2017 15:10
   13/07/2017 15:23
   13/07/2017 14:56
   13/07/2017 15:15
   13/07/2017 15:15
   13/07/2017 14:56
   13/07/2017 14:56
   13/07/2017 14:56
   13/07/2017 15:15
   13/07/2017 15:02
   13/07/2017 15:10

df <-  read.csv2(file="DF.csv")


df <- as.POSIXct(df$C1, format="%H:%M:%S", tz="GMT")

You need to `format` the variable after reading it as `POSIXct`. Example: `as.POSIXct(df$C1, format = "%d/%m/%Y %H:%M") %>% format("%H:%M:%S")` — amatsuo_net, Jul 13 '17 at 08:08
Once you use `format()` function, the output is a string of HMS, so that can't happen. — amatsuo_net, Jul 13 '17 at 08:35
Possible duplicate of [date time conversion and extract only time](https://stackoverflow.com/questions/31876962/date-time-conversion-and-extract-only-time) — JanLauGe, Jul 13 '17 at 08:54

score 3 · Answer 1 · answered Jul 13 '17 at 08:31

3

library(lubridate)
df$C1 <- hm(df$C1)

answered Jul 13 '17 at 08:31

Kalees Waran

659
6
13

Lorenzo Benassi · Accepted Answer · 2017-07-13T09:44:51.343

I tried to replicate your data frame and apply the function as.POSIXct() to better replicate your situation.

You can use the strftime() function to split the column and then the function times() to create a chronological object.

df = data.frame(C1 = c("13/07/2017 15:15","13/07/2017 15:02","13/07/2017 14:40","13/07/2017 15:15",
                   "13/07/2017 15:10","13/07/2017 15:23","13/07/2017 14:56","13/07/2017 15:15",
                   "13/07/2017 15:15","13/07/2017 14:56","13/07/2017 14:56","13/07/2017 14:56",
                   "13/07/2017 15:15","13/07/2017 15:02","13/07/2017 15:10"))  #replicate data frame
df <- as.POSIXct(df$C1, format = "%d/%m/%Y %H:%M") #apply  function to create a POSIXct object

Then the function you need to apply to your data frame it's the following:

library(chron)
time <- times(strftime(df, format="%H:%M:%S")) #select only time and create a times object

This is results:

time
[1] 15:15:00 15:02:00 14:40:00 15:15:00 15:10:00 15:23:00 14:56:00 15:15:00 15:15:00 14:56:00 14:56:00 14:56:00 15:15:00 15:02:00 15:10:00
class(time)
[1] "times"

how to read only time in a data frame

2 Answers2