Change from Date and Hour Format to Numeric Format

Change from date time to numeric AND back to date time in R

I think it is just a problem of specifying time zones :

x <- as.POSIXct("9/27/2011  15:33:00", format="%m/%d/%Y  %H:%M:%S")
> as.POSIXct(as.numeric(x), origin="1970-01-01",tz="EST") # as.numeric(x)=1317130380
[1] "2011-09-27 08:33:00 EST"

but :

x <- as.POSIXct("9/27/2011  15:33:00", format="%m/%d/%Y  %H:%M:%S",tz="EST")
> as.POSIXct(as.numeric(x), origin="1970-01-01",tz="EST") # as.numeric(x)=1317155580
[1] "2011-09-27 15:33:00 EST"

remark : I simplified 03:33:00 PM in 15:33:00

Issue in converting date format to numeric format in R

It's pretty easy as you have a standard format (see ISO 8601) which inter alia the anytime package supports (and it supports other, somewhat regular formats):

R> library(anytime)
R> at <- anytime("2016-08-30 10:46:46.810")
R> at
[1] "2016-08-30 10:46:46.80 CDT"
R> ad <- anydate("2016-08-30 10:46:46.810")
R> ad
[1] "2016-08-30"
R> 

The key, though, is to understand the relationship between the underlying date formats. You will have to read and try a bit more on that. Here, in essence we just have

R> as.Date(anytime("2016-08-30 10:46:46.810"))
[1] "2016-08-30"
R> 

The anytime package has a few other tricks such as automagic conversion from integer, character, factor, ordered, ...

As for the second part of your question, your were so close and then you spoiled it again with format() creating a character representation.

You almost always want Date representation instead:

R> ad <- as.Date(anytime("2016-08-30 10:46:46.810"))
R> as.integer(ad)
[1] 17043
R> as.numeric(ad)
[1] 17043
R> ad + 1:3
[1] "2016-08-31" "2016-09-01" "2016-09-02"
R> 

Convert date and time which is in character to numeric

You need to remove seconds from time formatting

 mk <- read.csv("mk.csv")

 head(mk)
  Label Value      Timestamp
1    W5 0.333 6/24/2017 0:00
2    W5 0.333 6/24/2017 0:30
3    W5 0.334 6/24/2017 1:00
4    W5 0.334 6/24/2017 1:30
5    W5 0.334 6/24/2017 2:00
6    W5 0.334 6/24/2017 2:30

 mk$Timestamp <- as.POSIXct(mk$Timestamp,format="%m/%d/%Y %H:%M")

 head(mk)
  Label Value           Timestamp
1    W5 0.333 2017-06-24 00:00:00
2    W5 0.333 2017-06-24 00:30:00
3    W5 0.334 2017-06-24 01:00:00
4    W5 0.334 2017-06-24 01:30:00
5    W5 0.334 2017-06-24 02:00:00
6    W5 0.334 2017-06-24 02:30:00

Then simply plot

ggplot(mk, aes(x=Timestamp, y=Value, colour=Label)) + geom_line()

Converting time format to numeric with R

If you just want to remove ":" , " ", and "-" from a character vector then this will suffice:

end <- gsub("[: -]", "" , begin, perl=TRUE)
#> end
#[1] "20010313103100"

You should read the section about 1/4 of the way down in ?regex about character classes. Since the "-" is special in that context as a range operator, it needs to be placed first or last.

After your edit then the answer is clearly what @joran wrote, except that you would need first to convert to a DateTime class:

 as.numeric(as.POSIXct(begin))
#[1] 984497460

The other point to make is that comparison operators do work for Date and DateTime classed variables, so the conversion may not be necessary at all. This compares 'begin' to a time one second later and correctly reports that begin is earlier:

as.POSIXct(begin) < as.POSIXct(begin) +1
 #[1] TRUE

How to convert time format in numeric in R

We could use lubridate.

library(dplyr)
library(lubridate)
df %>% 
  mutate(across(ends_with("time"),  ymd_hms)) %>% 
  mutate(across(ends_with("time"), ~ as.numeric(.), .names = "{.col}.{.fn}"))

Output:

   trip_id start_time          end_time            start_time.1 end_time.1
     <dbl> <dttm>              <dttm>                     <dbl>      <dbl>
 1       1 2020-10-05 11:11:36 2020-10-05 12:12:54   1601896296 1601899974
 2       2 2020-10-05 16:09:16 2020-10-05 20:00:42   1601914156 1601928042
 3       3 2020-10-05 09:16:33 2020-10-05 11:16:27   1601889393 1601896587
 4       4 2020-10-05 14:16:38 2020-10-05 14:37:38   1601907398 1601908658
 5       5 2020-10-05 13:08:16 2020-10-05 13:13:16   1601903296 1601903596
 6       6 2020-10-05 11:02:23 2020-10-05 13:04:16   1601895743 1601903056
 7       7 2020-10-05 13:15:19 2020-10-05 15:54:19   1601903719 1601913259
 8   56562 2020-10-09 11:05:25 2020-10-09 13:37:44   1602241525 1602250664
 9   56563 2020-10-09 14:11:30 2020-10-09 14:12:30   1602252690 1602252750
10   56564 2020-10-09 16:00:40 2020-10-09 16:46:58   1602259240 1602262018

How to convert numeric time into date, time format in R

Big fan of parse_date_time from lubridate and the timetk package:

library(tidyverse)
library(lubridate)
library(timetk)

test %>%
  mutate(date = parse_date_time(paste(date, str_pad(time, 4, side = "left", pad = "0")), "YmdHM")) %>%
  select(-time) %>%
  tk_xts(silent = T)

                     price
1990-01-02 09:30:00 353.40
1990-01-02 09:31:00 353.25
1990-01-02 09:32:00 353.02
1990-01-02 09:33:00 352.97
1990-01-02 09:34:00 352.81
1990-01-02 09:35:00 352.74

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