Add a crossing of two factors to a data frame
add_factor_crossing(data, fac1, fac2, new_name)a data frame
name of first factor, must be found in df
name of second factor, must be found in df
name of the new factor
a data frame
Other data frame handling functions:
add_dis_age(),
add_factor(),
adjusted_c_hat(),
new_x(),
split()