Identify the independent variable column(s) of a summary

A summary carries no marker for its independent variable: it is whatever column is not one of the standard summary columns. Two companion columns have to be left out of that by-exclusion test, since each sits next to the column it derives from and would otherwise pass for a second independent variable: .value, the int_plot_html data column, and <indep>_original, which add_n_to_label() adds to hold the labels before their (N = ...) suffix (#620).

Usage

get_indep_col_names(data)

Arguments

data

A summary, or the data of a plot built from one

Value

Character vector of column names, empty when there is none