Get the x-y coordinates of a dendrogram's nodes. Can be used to add text or images on the tree.

get_nodes_xy(
dend,
type = c("rectangle", "triangle"),
center = FALSE,
horiz = FALSE,
...
)

## Source

This is a striped down version of the function plot.dendrogram. It performs (almost) the same task, only it does not do any plotting but it does save the x-y coordiantes of the nodes.

## Arguments

dend

a dendrogram object

type

type of plot.

center

logical; if TRUE, nodes are plotted centered with respect to the leaves in the branch. Otherwise (default), plot them in the middle of all direct child nodes.

horiz

logical indicating if the dendrogram should be drawn horizontally or not.

...

not used

## Value

A 2-dimensional matrix, with rows as the number of nodes, and the first column is the x location, while the second is the y location.

## Examples

if (FALSE) {

# If we would like to see the numbers from plot:
# ?getOption("verbose")
# options(verbose=TRUE)
# options(verbose=FALSE)

# -----
# Draw a depth first search illustration
# -----

dend <- 1:5 %>%
dist() %>%
hclust() %>%
as.dendrogram()
get_nodes_xy(dend)

# polygon(get_nodes_xy(dend), col = 2)
plot(dend,
leaflab = "none",
main = "Depth-first search in a dendrogram"
)
xy <- get_nodes_xy(dend)
for (i in 1:(nrow(xy) - 1)) {
arrows(xy[i, 1], xy[i, 2],
angle = 17,
length = .5,
xy[i + 1, 1], xy[i + 1, 2],
lty = 1, col = 3, lwd = 1.5
)
}
points(xy, pch = 19, cex = 4)
text(xy, labels = 1:nnodes(dend), cex = 1.2, col = "white", adj = c(0.4, 0.4))
}