ida.data.frame objects provide many methods that will behave exactly like or very
similar to methods defined on a regular data.frame. The following is a list of
currently supported methods: as.data.frame, sd, max, mean, min, length, print, names, colnames,
summary, NROW, NCOL, dim, var, head, hist, cor, cov. Furthermore, the $ and [ operators allow you
to select columns and rows and the $<- operator will allow you to add columns. For details see
the documentation of ida.data.frame.