get_cnd_df_cnd_sum: Get the summary of the conditioning vector from a conditioned data frame
Description
get_cnd_df_cnd_sum() extracts the tally of the conditioning vector from a
conditioned data frame.
Usage
get_cnd_df_cnd_sum(dat)
Value
A vector of three elements providing the sum of TRUE, FALSE, and
NA values in the conditioning vector (cnd), or NULL if dat is not
a conditioned data frame (cnd_df).