summarize.by.factors. A table is
generated to display the estimated average rate of
missingness for every point in the space of categorical
covariates. Reference levels may be selected for each
category to reduce the size of the tablerates.by.category(x, reference.levels = c())lllcrc or vgam.crcformat.data. For example, if sex is a variable,
two columns x.dis.1.M and x.dis.1.F may be
included in the table un