complete                Complete a data frame with missing combinations
                        of data.
drop_na                 Drop rows containing missing values
expand                  Expand data frame to include all combinations
                        of values
extract                 Extract one column into multiple columns.
fill                    Fill in missing values.
full_seq                Create the full sequence of values in a vector.
gather                  Gather columns into key-value pairs.
nest                    Nest repeated values in a list-variable.
replace_na              Replace missing values
separate                Separate one column into multiple columns.
separate_rows           Separate a collapsed column into multiple rows.
smiths                  Some data about the Smith family.
spread                  Spread a key-value pair across multiple
                        columns.
table1                  Example tabular representations
uncount                 "Uncount" a data frame
unite                   Unite multiple columns into one.
unnest                  Unnest a list column.
who                     World Health Organization TB data
