ymd {lubridate} | R Documentation

## Parse dates with year, month, and day components

### Description

Transforms dates stored in character and numeric vectors to Date or POSIXct objects (see `tz` argument). These functions recognize arbitrary non-digit separators as well as no separator. As long as the order of formats is correct, these functions will parse dates correctly even when the input vectors contain differently formatted dates. See examples.

### Usage

    ymd(..., quiet = FALSE, tz = NULL, locale = Sys.getlocale("LC_TIME"),
      truncated = 0)

    ydm(..., quiet = FALSE, tz = NULL, locale = Sys.getlocale("LC_TIME"),
      truncated = 0)

    mdy(..., quiet = FALSE, tz = NULL, locale = Sys.getlocale("LC_TIME"),
      truncated = 0)

    myd(..., quiet = FALSE, tz = NULL, locale = Sys.getlocale("LC_TIME"),
      truncated = 0)

    dmy(..., quiet = FALSE, tz = NULL, locale = Sys.getlocale("LC_TIME"),
      truncated = 0)

    dym(..., quiet = FALSE, tz = NULL, locale = Sys.getlocale("LC_TIME"),
      truncated = 0)

    yq(..., quiet = FALSE, tz = NULL, locale = Sys.getlocale("LC_TIME"))

### Arguments

`...` | a character or numeric vector of suspected dates
`quiet` | logical. When TRUE function evalueates without displaying customary messages.
`tz` | Time zone indicator. If NULL (default) a Date object is returned. Otherwise a POSIXct with time zone attribute set to `tz`.
`locale` | locale to be used, see locales. On linux systems you can use `system("locale -a")` to list all the installed locales.
`truncated` | integer. Number of formats that can be truncated.

### Details

In case of heterogeneous date formats `ymd()` family guesses formats based on a sub-set of the input vector. If the input vector contains many missing values or non-date strings, the sub-set might not contain meaningful dates and the date-time format won't be guessed resulting in "All formats failed to parse" error. In such cases please see `parse_date_time()` for a more flexible parsing interface.

If the `truncated` parameter is non-zero, the `ymd` functions also check for truncated formats. For example `ymd()` with `truncated = 2` will also parse incomplete dates like `2012-06` and `2012`.

NOTE: The `ymd` family of functions are based on `parse_date_time()` and thus directly drop to the internal C parser for numeric months, but use R's `strptime()` for alphabetic months. This implies that some of the `strptime()`'s limitations are inherited by lubridate's parser. For example, truncated formats (like `%Y-%b`) will not be parsed. Numeric truncated formats (like `%Y-%m`) are handled correctly by lubridate's C parser.

As of version 1.3.0, lubridate's parse functions no longer return a message that displays which format they used to parse their input. You can change this by setting the `lubridate.verbose` option to `TRUE` with `options(lubridate.verbose = TRUE)`.

### Value

a vector of class POSIXct if tz argument is non-NULL or Date if tz is NULL (default)

### See Also

`parse_date_time()` for an even more flexible low level mechanism.

### Examples

    x <- c("09-01-01", "09-01-02", "09-01-03")
    ymd(x)
    x <- c("2009-01-01", "2009-01-02", "2009-01-03")
    ymd(x)
    ymd(090101, 90102)
    now() > ymd(20090101)
    ## TRUE
    dmy(010210)
    mdy(010210)

    ## heterogenuous formats in a single vector:
    x <- c(20090101, "2009-01-02", "2009 01 03", "2009-1-4",
           "2009-1, 5", "Created on 2009 1 6", "200901 !!! 07")
    ymd(x)

    ## What lubridate might not handle:

    ## Extremely weird cases when one of the separators is "" and some of the
    ## formats are not in double digits might not be parsed correctly:
    ## Not run: ymd("201002-01", "201002-1", "20102-1")
    dmy("0312-2010", "312-2010")
    ## End(Not run)

[Package lubridate version 1.7.4 Index]