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Collapse Table Dimensions by Remapping Factor Levels

Source: R/collapseTable.R
collapseTable.Rd

Aggregates a table or ftable object by reassigning the levels of one or more dimensions according to user-supplied mappings, and summing the frequencies within each resulting level combination.

Usage

collapseTable(x, ..., strict = TRUE)

Arguments

x

a table or ftable object with named dimensions.

...

named or unnamed mapping vectors specifying how levels of each dimension should be collapsed. Each mapping vector must have length equal to the number of levels in the corresponding dimension.

strict

logical (default TRUE). Controls error handling.

Value

a collapsed table object with updated dimensions and aggregated frequencies.

Details

Mapping vectors define how factor levels are reassigned. Element i specifies the new label for the i-th original level. Repeated values in a mapping vector cause the corresponding levels to be merged.

Argument matching

  • Named arguments are matched to dimensions by name (e.g., age = c("young", "adult")).

  • Unnamed arguments are assigned to dimensions in order.

  • Mixed usage assigns named arguments first, then remaining unnamed arguments in order.

Constraints

  • Each dimension may be specified at most once.

  • Mapping vectors must have the same length as the number of levels of the corresponding dimension.

  • NA values in mapping vectors are not allowed.

Level ordering The order of the resulting levels follows the first occurrence of each value in the mapping vector.

Error handling

  • If strict = TRUE, unknown dimension names result in an error, and positional assignment of unnamed arguments produces a warning.

  • If strict = FALSE, unknown dimensions produce a warning (and are ignored), and positional assignment is silent.

See also

Other data.reshape: long-wide-reshape, splitAt(), splitX(), untable()

Examples

tab <- xtabs(~ gear + cyl, data = mtcars)
tab
#>     cyl
#> gear  4  6  8
#>    3  1  2 12
#>    4  8  4  0
#>    5  2  1  2

# merge the 4- and 6-cylinder categories
collapseTable(tab, cyl = c("le6", "le6", "8"))
#>     cyl
#> gear le6  8
#>    3   3 12
#>    4  12  0
#>    5   3  2

# positional assignment (first dimension), silent with strict = FALSE
collapseTable(tab, c("3-4", "3-4", "5"), strict = FALSE)
#>      cyl
#> gear   4  6  8
#>   3-4  9  6 12
#>   5    2  1  2