find_and_transform_dates {dataPreparation} R Documentation

## Identify date columns

### Description

Find and transform dates that are hidden in a character column.
It use a bunch of default formats, and you can also add your own formats.

### Usage

find_and_transform_dates(
data_set,
cols = "auto",
formats = NULL,
n_test = 30,
ambiguities = "IGNORE",
verbose = TRUE
)


### Arguments

 data_set Matrix, data.frame or data.table cols List of column(s) name(s) of data_set to look into. To check all all columns, set it to "auto". (characters, default to "auto") formats List of additional Date formats to check (see strptime) n_test Number of non-null rows on which to test (numeric, default to 30) ambiguities How ambiguities should be treated (see details in ambiguities section) (character, default to IGNORE) verbose Should the algorithm talk? (Logical, default to TRUE)

### Details

This function is using identify_dates to find formats. Please see it's documentation. In case identify_dates doesn't find wanted formats you can either provide format in param formats or use set_col_as_date to force transformation.

### Value

data_set set (as a data.table) with identified dates transformed by reference.

### Ambiguity

Ambiguities are often present in dates. For example, in date: 2017/01/01, there is no way to know if format is YYYY/MM/DD or YYYY/DD/MM.
Some times ambiguity can be solved by a human. For example 17/12/31, a human might guess that it is YY/MM/DD, but there is no sure way to know.
To be safe, find_and_transform_dates doesn't try to guess ambiguities.
To answer ambiguities problem, param ambiguities is now available. It can take one of the following values

• IGNORE function will then take the first format which match (fast, but can make some mistakes)

• WARN function will try all format and tell you - via prints - that there are multiple matches (and won't perform date transformation)

• SOLVE function will try to solve ambiguity by going through more lines, so will be slower. If it is able to solve it, it will transform the column, if not it will print the various acceptable formats.

If there are some columns that have no chance to be a match think of removing them from cols to save some computation time.

### Examples

# Load exemple set
# using the find_and_transform_dates

# Example with ambiguities
## Not run:
require(data.table)
messy_adult$date1 = sort(messy_adult$date1, na.last = TRUE)