S3 details for xy objects
new_wk_xy(x = list(x = double(), y = double()))new_wk_xyz(x = list(x = double(), y = double(), z = double()))
new_wk_xym(x = list(x = double(), y = double(), m = double()))
new_wk_xyzm(x = list(x = double(), y = double(), z = double(), m = double()))
validate_wk_xy(x)
validate_wk_xyz(x)
validate_wk_xym(x)
validate_wk_xyzm(x)
A xy()
object.