map_unique: Report unique values for each column of a data.frame
In allenbaron/JABmisc: Utility Functions for Data Analysis

For each column in a data.frame, map_unique() shows the number of unique values and, optionally, the values themselves.

1	map_unique(df, vals = "as_string", sep = " \| ", ignore_NA = TRUE)

`df`	a data.frame
`vals`	a string describing how to display unique values; one of: "as_string" (default): for values as a concatenated string (for quick viewing) "as_list": for values as a column of lists "both": for concatenated string AND list columns "none"
`sep`	a character string to separate the values; used with "as_string"
`ignore_NA`	logical; whether to include missing (`NA`) values in report; affects both count and values displayed