get_confidential.RdGet the number of unique records per group, where the groups are defined
using the interaction of all columns listed in xvar.
Typically, less than three entries leads to the exposure of
confidential data. This function allows one to check to see the
number of unique labels (e.g., vessel names) within various
categories (e.g., combinations of month and year) is less than three.
Data can then be subset based on the new column called ngroups.
get_confidential(data, xvar, yvar = "VESSEL")A new column is added to the input data frame
called ngroups that provides the number of unique yvar entries
for each grouping.
If you want to use two variables for yvar, then you will need to pre-process
your data. The interaction function will be helpful, in that it can take
any number of columns and create a new column that is combination of everything
that you want. This option is better than using paste to combine columns.
You will not always want the interaction though, and sometimes you might want
to use ifelse calls to combine columns.
For example, with hake, catcher boats deliver to motherships and each type of
vessel has its own name in the data frame. If the catcher boat column entry is
NA then you would assume that a name would be present in the mothership column
because it might be a catcher-processor vessel that doesn't need a catcher boat.
So, if is.na(data[, "catcherboat"]) then data[, "mothership"].