On https://research.cbs.nl/casc/glossary.htm one can found the
“official” definition of microaggregation:
Records are grouped based on a proximity measure of variables of interest,
and the same small groups of records are used in calculating aggregates for
those variables. The aggregates are released instead of the individual
record values.
The recommended method is “rmd” which forms the proximity using
multivariate distances based on robust methods. It is an extension of the
well-known method “mdav”. However, when computational speed is
important, method “mdav” is the preferable choice.
While for the proximity measure very different concepts can be used, the
aggregation itself is naturally done with the arithmetic mean.
Nevertheless, other measures of location can be used for aggregation,
especially when the group size for aggregation has been taken higher than 3.
Since the median seems to be unsuitable for microaggregation because of
being highly robust, other mesures which are included can be chosen. If a
complex sample survey is microaggregated, the corresponding sampling weights
should be determined to either aggregate the values by the weighted
arithmetic mean or the weighted median.
This function contains also a method with which the data can be clustered
with a variety of different clustering algorithms. Clustering observations
before applying microaggregation might be useful. Note, that the data are
automatically standardised before clustering.
The usage of clustering method ‘Mclust’ requires package mclust02,
which must be loaded first. The package is not loaded automatically, since
the package is not under GPL but comes with a different licence.
The are also some projection methods for microaggregation included. The
robust version ‘pppca’ or ‘clustpppca’ (clustering at first)
are fast implementations and provide almost everytime the best results.
Univariate statistics are preserved best with the individual ranking method
(we called them ‘onedims’, however, often this method is named
‘individual ranking’), but multivariate statistics are strong
affected.
With method ‘simple’ one can apply microaggregation directly on the
(unsorted) data. It is useful for the comparison with other methods as a
benchmark, i.e. replies the question how much better is a sorting of the
data before aggregation.