Creating a Specific Sequence of Date/Times in R

Creating a specific sequence of date/times in R

I would strongly recommend you to use the POSIXct datatype. This way you can use seq without any problems and use those data however you want.

start <- as.POSIXct("2012-01-15")
interval <- 60

end <- start + as.difftime(1, units="days")

seq(from=start, by=interval*60, to=end)

Now you can do whatever you want with your vector of timestamps.

How to generate a sequence of dates and times with a specific start date/time in R

No need for lubridate, just,R code:

x <- data.frame(date = c(as.POSIXct("2018-01-01 00:00:00"), rep(NA,10)))
startDate <- x[["date"]][1]
x[["date2"]] <- startDate + (seq_len(nrow(x)) - 1)
x
#         date               date2
# 1  2018-01-01 2018-01-01 00:00:00
# 2        <NA> 2018-01-01 00:00:01
# 3        <NA> 2018-01-01 00:00:02
# 4        <NA> 2018-01-01 00:00:03
# 5        <NA> 2018-01-01 00:00:04
# 6        <NA> 2018-01-01 00:00:05
# 7        <NA> 2018-01-01 00:00:06
# 8        <NA> 2018-01-01 00:00:07
# 9        <NA> 2018-01-01 00:00:08
# 10       <NA> 2018-01-01 00:00:09
# 11       <NA> 2018-01-01 00:00:10

Create a sequence of times in R?

We can use seq :

format(seq(as.POSIXct('00:00', format = "%H:%M", tz = "UTC"), 
           as.POSIXct(Sys.Date() + 1), by = '10 mins'), "%I:%M%p")

#[1] "12:00AM" "12:10AM" "12:20AM" "12:30AM" "12:40AM" "12:50AM" "01:00AM ...
#[141] "11:20PM" "11:30PM" "11:40PM" "11:50PM" "12:00AM"

Make sure you have the correct locale or set it via :

Sys.setlocale("LC_TIME", "en_US.UTF-8")!

Create a regular sequence of date-times (POSIXct) using seq()

There is a seq() method for objects of class "POSIXt" which is the super class of the "POSIXlt" and "POSIXct" classes. As such you don't need to do any conversion.

> now <- Sys.time()
> tseq <- seq(from = now, length.out = 100, by = "mins")
> length(tseq)
[1] 100
> head(tseq)
[1] "2012-01-19 10:52:38 GMT" "2012-01-19 10:53:38 GMT"
[3] "2012-01-19 10:54:38 GMT" "2012-01-19 10:55:38 GMT"
[5] "2012-01-19 10:56:38 GMT" "2012-01-19 10:57:38 GMT"

Create a sequence of dates and store in a data frame with a column name

There are lot of ways to do that, since you used data.frame :

library(lubridate)
library(magrittr)

seq.Date(from = as.Date(today()- days(7)),
        to = as.Date(today()),
        by = "day")  %>%
  data.frame(DATE = .)

#        DATE
#1 2021-04-23
#2 2021-04-24
#3 2021-04-25
#4 2021-04-26
#5 2021-04-27
#6 2021-04-28
#7 2021-04-29
#8 2021-04-30

Creating a unique sequence of dates

As I noted in my comment, seq has method for dates, seq.Date:

seq(as.Date('2011-01-01'),as.Date('2011-01-31'),by = 1)
 [1] "2011-01-01" "2011-01-02" "2011-01-03" "2011-01-04" "2011-01-05" "2011-01-06" "2011-01-07" "2011-01-08"
 [9] "2011-01-09" "2011-01-10" "2011-01-11" "2011-01-12" "2011-01-13" "2011-01-14" "2011-01-15" "2011-01-16"
[17] "2011-01-17" "2011-01-18" "2011-01-19" "2011-01-20" "2011-01-21" "2011-01-22" "2011-01-23" "2011-01-24"
[25] "2011-01-25" "2011-01-26" "2011-01-27" "2011-01-28" "2011-01-29" "2011-01-30" "2011-01-31"

Create sequence of dates and times in R without time zones

The problem is that since it is adjusting for BST, I get two values for certain dates in October.

That's because the 'fall back' (mnemonic for daylight savings times adjustment adding an hour in the fall) happens under human time and that is what you get by default unless you override it.

R> seq(as.POSIXlt("2012-10-28 00:00:00", tz="UTC"), 
+      as.POSIXlt("2012-10-28 03:00:00", tz="UTC"), by="15 min")
 [1] "2012-10-28 00:00:00 UTC" "2012-10-28 00:15:00 UTC"
 [3] "2012-10-28 00:30:00 UTC" "2012-10-28 00:45:00 UTC"
 [5] "2012-10-28 01:00:00 UTC" "2012-10-28 01:15:00 UTC"
 [7] "2012-10-28 01:30:00 UTC" "2012-10-28 01:45:00 UTC"
 [9] "2012-10-28 02:00:00 UTC" "2012-10-28 02:15:00 UTC"
[11] "2012-10-28 02:30:00 UTC" "2012-10-28 02:45:00 UTC"
[13] "2012-10-28 03:00:00 UTC"
R> 

The example I show here covers the same subset as above but without the fall back as we now impose UTC as a time zone. And UTC has be construction no daylight savings adjustment.

How to use seq() to create column of date/times with increments of milliseconds (deciseconds)

This might work for you:

library(lubridate)
df <- data.frame(ID = 1:4, 
                 CH_1 = rep(c(-10096, -10088, -10084, -10088), 4),
                 CH_2 = rep(c(-11940, -11964, -11940, -11956), 4),
                 date_time = c("2018-07-24 10:45:01.1", rep(NA, 15)))

df$date_time <- as.POSIXct(df$date_time, format= "%F %H:%M:%OS2", tz = "UTC")
df$date_time <- seq(from = df$date_time[1], to = df$date_time[1] + (nrow(df)-1)*0.1, by = 0.10)
format(df$date_time, "%OS3")

Create sequence of date on every last day of month

If you want last day of month, instead of start from 2018-01-31, try

seq(as.Date("2018-02-01",format="%Y-%m-%d"),by="month",length.out=6) -1
[1] "2018-01-31" "2018-02-28" "2018-03-31" "2018-04-30" "2018-05-31" "2018-06-30"

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