is about contingency table 2 Orlaith Burke Alejandra Gonzalez-Beltran Philippe Rocca-Serra STATO, adapted from wikipedia (http://en.wikipedia.org/wiki/Contingency_table) a contigency table is a data item which displays the (multivariate) frequency distribution of the possible values of categorical variables. The first row of the table corresponds to categories of one categorical variable, the first column of the table corresponds to categories of the other categorical variable, the cells corresponding to each combination of categories is filled with the observed occurences in the sample being considered. The table also contains marginal total (marginal sums) and grand total of the occurences The term contingency table was first used by Karl Pearson in "On the Theory of Contingency and Its Relation to Association and Normal Correlation", part of the Drapers' Company Research Memoirs Biometric Series I published in 1904. 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 categorical variable matrix ready for release