Extract time (HMS) from lubridate date time object? - r

Question

I have the following datetime:
t <- "2018-05-01 23:02:50 UTC"
I want to split it to time and date.
When I apply date(t) I get the date part.
But when I use lubridate's hms, parse_date_time and other functions to do this in "HMS" order I get NA.
I have checked other answers here on SOF but for some reason it gives me NA.
Please advise how to extract it.
I want to understand why:
strftime(t, format="%H:%M:%S")
will do the job but what I am missing in lubridate::hms or parse_date_time?

Answer 1

Is this what you were looking for? It can now be done more simply with hms::as_hms.
> library(lubridate)
> library(hms)
> as_hms(ymd_hms("2018-05-01 23:02:50 UTC"))
23:02:50
> t <- "2018-05-01 23:02:50 UTC"
> as_hms(ymd_hms(t))
23:02:50

Answer 2

My solution is to install library(anytime):
date <- anytime::anydate(t)
time <- strftime(t, format="%H:%M:%S")

Answer 3

What you are missing in lubridate's hms() is that it expects "a character vector of hour minute second triples" as an argument. There's no provision for handling a string which also contains date info. Hence, the output of Sys.Date() or lubridate::now() doesn't work as input to lubridate::hms().
In case you want a tidyverse solution, here's one:
library(tidyverse)
library(lubridate)
now()
#> [1] "2018-08-13 16:41:31 BST"
get_time <- function(time = now()) {
time %>%
str_split(" ") %>%
map_chr(2) %>%
hms()
}
get_time()
#> [1] "16H 41M 31S"
get_time("2018-05-01 23:02:50 UTC")
#> [1] "23H 2M 50S"
Created on 2018-08-13 by the reprex package (v0.2.0).

Answer 4

Something like this?
library(hms)
t <- "2018-05-01 23:02:50 UTC"
unlist(strsplit(t," "))[2]%>%hms::parse_hms()

Answer 5

Here is a solution without including just another package (hms on top of lubridate):
t <- "2018-05-01 23:02:50 UTC"
sprintf("%02d:%02d:%02d", hour(t), minute(t), second(t))
"23:02:50"

Answer 6

The fucntion in Lubridate package exists, it is called "hour()", here the official guide:
https://lubridate.tidyverse.org/reference/hour
t <- "2018-05-01 23:02:50 UTC"
lubridate::hour(t)

Answer 7

Posting a solution that I have used to extract either ymd or the hms independently after a lubridate conversion. I noticed OP mentioned wanting to separate both time and date so for future SO users who may find themselves here I included the regex's used for both below. assuming df contains a column called date where time is formated ymd_hms like so "2018-05-01 23:02:50 UTC":
library(stringr)
df <- df %>%
mutate(
time = str_extract(date, "[0-9]{2}:[0-9]{2}:[0-9]{2}") #to extract hms time
day = str_extract(date, "[0-9]{4}-[0-9]{2}-[0-9]{2}") #to extract ymd time
)