Change day of the month in a Date to first day (01)

Question

I want to set the day of month in a Date to start date of current month (01). Now I use the following:

currentDate <- Sys.Date()  #for getting current system date eg:2012-11-06
formatDate <- format(currentDate, "%Y-%m")  #it return 2012-11
startDate <- as.Date(paste(formatDate, "-01", sep = ""))
# 2012-11-01 

Is there any easy way to do this?

Solution 1

Yes, there is a one-liner for that using function cut:

cut(Sys.Date(), "month")
[1] 2012-11-01
Levels: 2012-11-01

Solution 2

Also one line using format function:

format(Sys.Date(),"01-%m-%Y")
[1] "01-06-2017"

Solution 3

lubridate's floor_date keeps it a Date

library(lubridate)

floor_date(Sys.Date(), "month")

Solution 4

Using lubridate (also work with sec, min, hour, mon, year etc.)

library(lubridate)

dt <- Sys.Date()
day(dt) <- 01

dt
# [1] "2018-01-01"

Solution 5

as.Date(paste0(format(Sys.Date(), "%Y-%m"), "-01"))

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Comments

[Admin]

If in Linux, you may use system("date",intern=T) to extract the date information as a string and then edit it.

[Joseph Wood]

This has the added benefit of keeping it in a date format as opposed to converting it to a factor via cut.

[Prradep]

class(format(Sys.Date(),"01-%m-%Y")) results as "character". But class(cut(Sys.Date(), "month")) results in "factor". So, bothe these approaches need to Date conversion apporach!

[sytech]

It would be useful to elaborate more on this solution, explaining how or why this solves the question being asked, or why it is better/different from the method described in the question or other answers.