CODEWITHSUNDEEP
rdateposixct
user25420086
user25420086

Reputation: 11

POSIX date formats

I am working under R and I have a date (format "2018-08-10") and a time (format "10:00:00"). Both are character strings. I need to calculate the beginning time of the event (time - 60 minutes) and pass it to the following format: 20180810T090000Z with year-month-day T hours minutes seconds.

I tried the following:

time <- "10:00:00"
J0 <- "2018-08-10"
library(lubridate)
beginningtime = as.character(hms(time) - minutes(60))
datestart = as.character.POSIXt(as.POSIXct(paste(J0, beginningtime)),
          format = "%Y%m%dT%H%M%S")

This gives me datestart in the following format : "20240301T000000", without taking the time into account.

I guess this relates to the output of as.POSIXct(paste(J0, beginningtime)), which returns: "2024-03-01 CET", without the beginning time.

Does anyone know how to do this? I'm new to POSIX objects, and I'm at a loss about how to combine all the variants of the as.POSIX functions in order to get the right output.

Upvotes: 1

Views: 153

Answers (2)

Andre Wildberg
Andre Wildberg

Reputation: 19088

With base R using as.POSIXct and format.Date

beginningtime <- as.POSIXct(paste(J0, time))

format.Date(beginningtime - 60*60, "%Y%m%dT%H%M%SZ")
[1] "20180810T090000Z"

Note that beginningtime is left as a Date object. IMO there seems no good reason to store the date as character since the format change happens afterwards anyways.

Upvotes: 3

Jonathan V. Sol&#243;rzano
Jonathan V. Sol&#243;rzano

Reputation: 5620

Using lubridate you can paste your J0 and time objects, and then use ymd_hms to convert it from character to date. Then, you can subtract 60 minutes and set your desired output format (with stamp) to the result.

library(lubridate)

# Create desired output format
datestamp <- stamp("2018-08-10T10:00:00Z")
# Paste ymd and hms, and convert to date 
date <- ymd_hms(paste(J0, time))
# Subtract 60 minutes
date <- date - minutes(60)
# Apply desired format
datestamp(date)

[1] "2018-08-10T09:00:00Z"

Upvotes: 2

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