skim-obj: Test if an object is compatible with `skimr`

Description

Objects within skimr are identified by a class, but they require additional attributes and data columns for all operations to succeed. These checks help ensure this. While they have some application externally, they are mostly used internally.

Usage

has_type_column(object)
has_variable_column(object)
has_skimr_attributes(object)
has_skim_type_attribute(object)
has_skimmers(object)
is_data_frame(object)
is_skim_df(object)
is_one_skim_df(object)
is_skim_list(object)
could_be_skim_df(object)
assert_is_skim_df(object)
assert_is_skim_list(object)
assert_is_one_skim_df(object)

Arguments

object: Any R object.

Functions

has_type_column(): Does the object have the skim_type column?
has_variable_column(): Does the object have the skim_variable column?
has_skimr_attributes(): Does the object have the appropriate skimr attributes?
has_skim_type_attribute(): Does the object have a skim_type attribute? This makes it a one_skim_df.
has_skimmers(): Does the object have skimmers?
is_data_frame(): Is the object a data frame?
is_skim_df(): Is the object a skim_df?
is_one_skim_df(): Is the object a one_skim_df? This is similar to a skim_df, but does not have the type column. That is stored as an attribute instead.
is_skim_list(): Is the object a skim_list?
could_be_skim_df(): Is this a data frame with skim_variable and skim_type columns?
assert_is_skim_df(): Stop if the object is not a skim_df.
assert_is_skim_list(): Stop if the object is not a skim_list.
assert_is_one_skim_df(): Stop if the object is not a one_skim_df.

Details

Most notably, a skim_df has columns skim_type and skim_variable. And has the following special attributes

data_rows: n rows in the original data
data_cols: original number of columns
df_name: name of the original data frame
dt_key: name of the key if original is a data.table
groups: if there were group variables
base_skimmers: names of functions applied to all skim types
skimmers_used: names of functions used to skim each type

The functions in these checks work like all.equal(). The return TRUE if the check passes, or otherwise notifies why the check failed. This makes them more useful when throwing errors.