Ordering by keeping defined groups together

This function modifies the order of a vector so that specified groups of elements remain together. This is useful for keeping specific dendrogram leaves together. The location of each group block is determined by the earliest member of that group in original vector. For elements not involved in any group, their relative order is unchanged.

Usage

group_constrained_order(x, groups, group_order = c("groups", "original"))

Arguments

x

The original vector of elements in order.

groups

The groups of elements that are to be kept together as a list of vectors. The groups must be disjoint.

group_order

The group internal order should follow the one in "groups" or the "original" order.

Value

A vector of the original elements where the specified groups of elements are kept together.

Examples

set.seed(123)

# data
mat <- matrix(rnorm(8 * 4), nrow = 8)
rownames(mat) <- LETTERS[1:8]

# hierarchical clustering
hc <- hclust(dist(mat))
plot(hc, main = "Original dendrogram")


# groups of leaves to keep together (may not be adjacent in dendrogram)
groups <- list(
  g1 = c("B", "F"),
  g2 = c("C", "D", "E")
)

# Dendrogram original order
orig_order <- hc$labels[hc$order]
orig_order
#> [1] "C" "F" "H" "B" "E" "A" "D" "G"

# Get group constrained order
new_order <-
  group_constrained_order(x = orig_order,
                          groups = groups,
                          group_order = "original")

new_order
#> [1] "C" "E" "D" "F" "B" "H" "A" "G"

# Reorder dendrogram labels
hc2 <- hc
hc2$order <- match(new_order, hc$labels)

plot(hc2, main = "Dendrogram with grouped leaves")