.preparedf              Prepare a data.frame for as.ffdf to not break
.upgradevmode           Upgrade vmode of ff column while stacking
Stack                   Stack Combine data frames with column names
                        that do not completely intersect
compact                 Compact a ff vector or ffdf data frame
ensureDate              Ensure that x is a Date
ffStack                 Merge a data.frame into an ffdf
                        data.frame-alike
find_min_vmode          Find minimum vmode for non-ff x
matrixIntegrate         Integrate matrices based on their dim names
padNA                   Add a length of NAs before or after x (used in
                        Stacking)
vecEqual                Test equality and order of a vector
vectorIntegrate         Integrate characters with careful ordering of
                        result
