Convert column by formating like date

[danut_horincas]

I want to convert 02/01/12 to 02-01-2012
where 02 are month 01 day and 2012 year

[FJCC]

It is simple enough to manipulate the initial string into another string but it will not have a Date value. Dates, as far as I know, are always displayed in R as YYYY-MM-DD.

DF <- data.frame(Date = c("02/01/12", "01/31/12"))
DF$Date <- sub("(\\d{2})/(\\d{2})/(\\d{2})", "\\1-\\2-20\\3", DF$Date)
DF
#>         Date
#> 1 02-01-2012
#> 2 01-31-2012

DF2 <- data.frame(Date = c("02/01/12", "01/31/12"))
DF2$Date <- as.Date(DF2$Date, format = "%m/%d/%y")
DF2
#>         Date
#> 1 2012-02-01
#> 2 2012-01-31

^{Created on 2023-02-19 with reprex v2.0.2}

[jrkrideau]

I think something like this will do it. However, it gives you a character variable not an actual date variable. Is this what you want?

library(lubridate)
(mydate <-  mdy("02/01/12"))

class(mydate)

(newdate  <- format(mydate, "%d/%m/%Y"))
class(newdate)      

[technocrat]

As well as @FJCC 's DF2

lubridate::mdy("02/01/12")
#> [1] "2012-02-01"

which is a date object.

Unless compelled to use a data frame or other R object for both calculation and presentation, it is far less trouble in the long run to process it through a report generator, such as {gt}, many of which have built-in functions to handle these chores. Too often, trying to mix data and presentation results in flawed solutions to both problems.