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In R, the as.Date() function can be used to convert numeric values to dates. This function takes a numeric vector as input and transforms it into an R date object. The as.Date() function also allows you to specify the format of the date string, so you can ensure that the date is converted into the correct format. Additionally, the as.POSIXct() function can be used to convert a numeric vector to a date in a specific time zone.
Often you may need to convert numbers to date formats in R. The easiest way to do this is by using the package, which has several helpful functions for dealing with dates in R.
This tutorial provides several examples of how to use these functions in practice.
Example 1: Convert Integers to Dates
The following code shows how to convert a column of integer values in a data frame to a date format by using the ymd() function:
library(lubridate) #create data frame df <- data.frame(date = c(20201022, 20201023, 20201026, 20201027, 20201028), sales = c(4, 7, 8, 9, 12)) #convert date column from numeric to year-month-date format df$date <- ymd(df$date) #view data frame df date sales 1 2020-10-22 4 2 2020-10-23 7 3 2020-10-26 8 4 2020-10-27 9 5 2020-10-28 12 #view class of date column class(df$date) [1] "Date"
Note that the lubridate package has several functions to handle different date formats.
For example, the following shows how to convert a column of integer values in a data frame to a date format by using the ydm() function:
library(lubridate) #create data frame df <- data.frame(date = c(20202210, 20202310, 20202610, 20202710, 20202810), sales = c(4, 7, 8, 9, 12)) #convert date column from numeric to year-month-date format df$date <- ydm(df$date) #view data frame df date sales 1 2020-10-22 4 2 2020-10-23 7 3 2020-10-26 8 4 2020-10-27 9 5 2020-10-28 12 #view class of date column class(df$date) [1] "Date"
Example 2: Convert Months & Years to Dates
The following code shows how to convert a column of numeric values that represent the number of months from January 1st, 2010 to a date format by using the months() function:
library(lubridate) #create data frame df <- data.frame(date = c(11, 15, 18, 22, 24), sales = c(4, 7, 8, 9, 12)) #convert date column from numeric to year-month-date format df$date <- as.Date('2010-01-01') + months(df$date) #view data frame df date sales 1 2010-12-01 4 2 2011-04-01 7 3 2011-07-01 8 4 2011-11-01 9 5 2012-01-01 12 #view class of date column class(df$date) [1] "Date"
And the following code shows how to convert a column of numeric values that represent the number of years from January 1st, 2010 to a date format by using the years() function:
library(lubridate) #create data frame df <- data.frame(date = c(11, 15, 18, 22, 24), sales = c(4, 7, 8, 9, 12)) #convert date column from numeric to year-month-date format df$date <- as.Date('2010-01-01') + years(df$date) #view data frame df date sales 1 2021-01-01 4 2 2025-01-01 7 3 2028-01-01 8 4 2032-01-01 9 5 2034-01-01 12 #view class of date column class(df$date) [1] "Date"
Bonus: Refer to to gain a better understanding of the functions available in the lubridate package.