Package {cldreducer}

cldreducer: Reduce Compact Letter Displays

Description

Reduces compact letter displays (CLDs) of all pairwise comparisons. A CLD gives two groups a common letter exactly when they are not significantly different. The package finds a display with the fewest letter assignments that keeps every one of these relationships. This is the assignment-minimum clique covering problem of Ennis, Fayle, and Ennis (2012) doi:10.1145/2133803.2275596, solved as a mixed-integer linear program with 'HiGHS'. Among the displays with the fewest assignments, it returns one fixed canonical display, so the result does not depend on the solver. The package includes the wheat yield example of Piepho (2004) doi:10.1198/1061860043515.

Author(s)

Maintainer: John Ennis john.m.ennis@aigora.com

Authors:

• John Ennis john.m.ennis@aigora.com

Other contributors:

• Aigora [copyright holder, funder]

See Also

Useful links:

• https://github.com/aigorahub/cld-reducer

• Report bugs at https://github.com/aigorahub/cld-reducer/issues

Piepho (2004) wheat yield example

Description

All 190 pairwise comparisons of 20 wheat treatments (varieties) from the CIMMYT multi-environment yield trial analyzed by Piepho (2004) and reproduced in Table 7 of Ennis, Fayle, and Ennis (2012). The comparisons are "not significantly different" for 172 pairs. The standard (maximal) display has 4 letters and 56 letter assignments. The reduced display from reduce_letters() also has 4 letters, but only 44 assignments.

Usage

piepho2004_wheat

Format

A data frame with 190 rows and 3 columns:

group1

Label of the first treatment, a character string from "1" to "20".

group2

Label of the second treatment.

significant

Logical. TRUE when the two treatments differ significantly.

Source

Piepho, H.-P. (2004). An algorithm for a letter-based representation of all-pairwise comparisons. Journal of Computational and Graphical Statistics, 13(2), 456-466. doi:10.1198/1061860043515, as tabulated in Ennis, Fayle, and Ennis (2012), Table 7. doi:10.1145/2133803.2275596

See Also

reduce_letters()

Examples

dim(piepho2004_wheat)
mean(!piepho2004_wheat$significant)

Reduce a compact letter display

Description

reduce_letters() and reduce_from_adjacency() find a compact letter display (CLD) with the fewest letter assignments in which two groups share a letter exactly when they are not significantly different. This is the assignment-minimum clique covering problem of Ennis, Fayle, and Ennis (2012). The programs are solved with 'HiGHS'. When several displays have the same, smallest number of assignments, the function returns the canonical one defined in the specification (docs/algorithm.md in the source repository), so the result does not depend on the solver. The same method is available in Python and JavaScript, and all three return the same display.

Usage

reduce_letters(
  pairs,
  means = NULL,
  group1 = "group1",
  group2 = "group2",
  significant = "significant",
  method = "assignment_minimum",
  time_limit = NULL,
  max_cliques = 10000L
)

reduce_from_adjacency(
  adjacency,
  groups = NULL,
  means = NULL,
  method = "assignment_minimum",
  time_limit = NULL,
  max_cliques = 10000L
)

Arguments

Value

An object of class cld_reduction, a list with

• letters: a named character vector with the display of each group (the letters of a group are joined with no separator when every letter is one character, and with spaces after Z, when letters like "AA" appear);

• assignments: a named list with the letters of each group as a character vector;

• stats: a list with assignments_before, assignments_after, reduction_pct (not rounded), num_letters_before, num_letters_after, num_groups, num_edges, solver_status, and objective;

• method, groups, relationship_preserved, and adjacency (a logical matrix).

The print() method shows the display and the counts, and as.data.frame() gives a table with the columns group, letters, and assignments.

Errors

Malformed input stops with a condition of class cldreducer_invalid_input. Solver problems, an invalid time_limit or max_cliques, and too many cliques stop with a condition of class cldreducer_solver_error. Both also have the class cldreducer_error.

References

Ennis, J. M., Fayle, C. M., and Ennis, D. M. (2012). Assignment-minimum clique coverings. ACM Journal of Experimental Algorithmics, 17, Article 1.5. doi:10.1145/2133803.2275596

Examples

# Five groups; groups 1 to 3, 2 to 4, and 3 to 5 do not differ.
result <- reduce_letters(simple_abc_pairs, simple_abc_means)
result$letters
result$stats$assignments_after

# The same example from the matrix of non-significant pairs
adjacency <- diag(TRUE, 5)
adjacency[cbind(c(1, 1, 2, 2, 3, 3, 4), c(2, 3, 3, 4, 4, 5, 5))] <- TRUE
adjacency <- adjacency | t(adjacency)
reduce_from_adjacency(adjacency, means = simple_abc_means)

Simple example: group means

Description

The group means that go with simple_abc_pairs. They fix the order of the groups and of the letters.

Usage

simple_abc_means

Format

A data frame with 5 rows and 2 columns: group (character labels "1" to "5") and mean (numeric).

Source

Ennis, J. M., Fayle, C. M., and Ennis, D. M. (2012). Assignment-minimum clique coverings. ACM Journal of Experimental Algorithmics, 17, Article 1.5. doi:10.1145/2133803.2275596

See Also

simple_abc_pairs, reduce_letters()

Examples

simple_abc_means

Simple example: pairwise results of five groups

Description

The five-group example of Ennis, Fayle, and Ennis (2012) in which the standard display ABC of one group reduces to AC. Groups 1 to 3, 2 to 4, and 3 to 5 do not differ significantly; all other pairs do.

Usage

simple_abc_pairs

Format

A data frame with 10 rows and 3 columns: group1 and group2 (character labels "1" to "5") and significant (logical).

Source

Ennis, J. M., Fayle, C. M., and Ennis, D. M. (2012). Assignment-minimum clique coverings. ACM Journal of Experimental Algorithmics, 17, Article 1.5. doi:10.1145/2133803.2275596

See Also

simple_abc_means, reduce_letters()

Examples

simple_abc_pairs
reduce_letters(simple_abc_pairs, simple_abc_means)$letters