Cell suppression with optional complementary suppression

Standard StatCan / open-data complementary-suppression: identifies counts below threshold, suppresses them by setting to NA, and (if return_complementary = TRUE) also suppresses the smallest other count in each affected row and column so the suppressed value can't be reconstructed from marginals.

Usage

morie_cell_suppress(tbl, threshold = 5, return_complementary = TRUE)

Arguments

tbl

A numeric matrix or 2-D table of counts. Will be coerced to matrix; row/column names are preserved.

threshold

Minimum count to remain unsuppressed. Default 5.

return_complementary

Logical; if TRUE (default), apply complementary suppression so primary-suppressed cells can't be recovered from marginal sums.

Value

A list with class "morie_cell_suppress":

suppressed

numeric matrix, suppressed cells set to NA.

primary_mask

logical matrix, TRUE for primary suppressions.

complementary_mask

logical matrix, TRUE for complementary suppressions (all FALSE when return_complementary = FALSE).

n_primary

integer.

n_complementary

integer.

threshold

the threshold used.

Details

Only finite numeric cells are eligible for suppression. NA cells in the input pass through unchanged.

Examples

tbl <- matrix(c(120, 3, 47, 88, 2, 99, 14, 51, 60),
  nrow = 3,
  dimnames = list(c("A", "B", "C"), c("X", "Y", "Z"))
)

# Default: primary suppression (cells 1..4) PLUS complementary suppression
# so a suppressed cell can't be recovered from row/column marginals.
res <- morie_cell_suppress(tbl, threshold = 5)
res$suppressed # NA where suppressed
#>     X  Y  Z
#> A 120 NA 14
#> B  NA NA NA
#> C  NA 99 60
res$n_primary # cells below threshold
#> [1] 2
res$n_complementary # extra cells hidden to protect the marginals
#> [1] 3
res$primary_mask
#>       X     Y     Z
#> A FALSE FALSE FALSE
#> B  TRUE  TRUE FALSE
#> C FALSE FALSE FALSE

# Turn complementary suppression off: only the small cells are hidden.
morie_cell_suppress(tbl,
  threshold = 5,
  return_complementary = FALSE
)$suppressed
#>     X  Y  Z
#> A 120 88 14
#> B  NA NA 51
#> C  47 99 60

# A higher threshold suppresses more cells.
morie_cell_suppress(tbl, threshold = 50)$n_primary
#> [1] 4

# Works on a 2-D table too; NA cells pass through untouched.
t2 <- as.table(matrix(c(2, 40, 30, 1), 2,
  dimnames = list(c("a", "b"), c("c", "d"))
))
morie_cell_suppress(t2, threshold = 5)$suppressed
#>   c d
#> a    
#> b