Makes sure the unit argument has one of the many available values.
Usage
checkUnit(unit)
Arguments
unit
[character] The string to check.
Value
[character] Either "o" or "w".
Details
Functions which produce contingency tables, coocc and summary, have an argument count which can take as many as eight different values which all point to just two unique behaviours. checkCount reduces this multitude to just the two meaningful values. It also throws an error if count is none of the eight possibilities.