Figure out margining variables. Given the variables that form the
rows and columns, and a set of desired margins, works out which ones
are possible. Variables that can't be margined over are dropped
silently.
Usage
margins(rows, cols, margins)
Arguments
col
a character vector of column names
row
a character vector of row names
margins
a character vector of variable names to margin over. Can be
any variable name in col or row, "grand_row" or
"grand_col". If TRUE will compute all possible margins.
Value
list of margining combinations, or NULL if none. These are
the combinations of variables that should have their values set to
`(all)`