era objectsTests whether an object is an era definition (an era object).
is_era() tests whether the object inherits from the S3 class era_yr.
is_valid_era() performs additional checks to determine whether the object
is well-formed (see details).
validate_era() throws an informative error message for invalid yrs.
is_era(x)validate_era(x)
is_valid_era(x)
is_era() and is_valid_era() return TRUE or FALSE.
validate_era() returns x invisibly, and is used for its side-effect of
throwing an informative error for invalid objects.
Object to test.
Valid era objects:
Must have all parameters set and not NA
Must have a character label parameter
Must have a numeric epoch parameter
Must have a character name parameter
Must have a character unit parameter that is one of the defined units
Must have a positive, integer scale parameter
Must have a direction parameter that is -1 (backwards) or 1 (forwards)
Other era helper functions:
era_parameters,
era_year_parameters,
era_year,
era,
is_era_year(),
is_yr(),
this_year()