is about specifies value of data item polychotomous variable dichotomous variable contingency table 2 by n contingency table 2 1 1 Philippe Rocca-Serra Orlaith Burke Alejandra Gonzalez-Beltran STATO a 2 by n contingency table is a contingency table built for one dichotomous variable (a categorical variable with only 2 outcomes) and one polychotomous variable (a polychomotomous variable with at least 2 outcomes) xtabs(formula = ~., data = parent.frame(), subset, sparse = FALSE, na.action, exclude = c(NA, NaN), drop.unused.levels = FALSE) http://stat.ethz.ch/R-manual/R-patched/library/stats/html/xtabs.html flat contingency tables: ftable(x, ...) http://stat.ethz.ch/R-manual/R-patched/library/stats/html/ftable.html ready for release