get_nodes_xy: Get the x-y coordinates of a dendrogram's nodes

In talgalili/dendextend: Extending 'dendrogram' Functionality in R

Get the x-y coordinates of a dendrogram's nodes

Description

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

Usage

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

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.

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.

See Also

get_nodes_attr, nnodes, nleaves

Examples

## Not run: 

# 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))

## End(Not run)

talgalili/dendextend documentation built on Jan. 27, 2024, 7:43 p.m.