Safety methods and suppression

Tau argus performs two kinds of suppression:

Primary suppression suppresses cells that violate safety rules.
Secondary suppression suppresses cells to protect other cells.

Safety rules

Cells directly violating one of these rules are protected during primary suppression.

Rule	Meaning
pa.percent_rule(p, n)	\(p%\)-rule
pa.dominance_rule(n, k)	\(N,K\) dominance rule
pa.frequency_rule(n)	Every cell needs \(n\) contributors

Suppression methods

Methods for secondary suppression aim to minimize the suppression cost while protecting the data.

Method	Description	Optimality	Speed
`pa.OPTIMAL`	Minimizes suppression costs (slowest)	High	Slow
`pa.MOD`	Protects sub-tables first and combines the result	Medium	Medium
`pa.GH`	Hypercube method	Low	Fast

Specifying rules

Safety rules can be set for individual observations. If some of the observations belong to the same unit, a safety rule can also be set on a holding-level. In that case the microdata should have a holding-column. If there is no holding information, safety rules can only be set on an individual level (per cell). Suppression methods are also be set per table.

import piargus as pa

table = pa.Table(response, explanatory, ...,
                 safety_rule={"individual": pa.percent_rule(20),
                              "holding": pa.percent_rule(30)},
                 suppress_method=pa.MODULAR)

If there are multiple linked tables, a safety rule can also be set on a job:

job = pa.Job(tables, ...,
             linked_suppress_method=pa.MODULAR)

Disclaimer

For a more official and theoretical explanation of suppression in argus, please consult the tau-manual. This page is meant as a practical overview, but is not authoritative.