# R/sort_smallest.R In dendsort: Modular Leaf Ordering Methods for Dendrogram Nodes

#### Documented in sort_smallest

```#' Sorting and reordering dendrogram nodes by the smallest value
#'
#' \code{sort_smallest} sorts a dendrogram object based on
#' the smallest distance in its subtrees, recursively.
#' The cluster with the smallest distance is placed on the left
#' side of branch.When a leaf merge with a cluster, the leaf is
#' placed on the right side.
#'
#' @param d A dendrogram object.\code{d}
#' @return output A sorted dendrogram object.
#' @keywords internal
#' @export sort_smallest
#' @aliases sort_smallest
#'
#' @examples
#' #generate sample data
#' set.seed(1234); par(mar=c(0,0,0,0))
#' x <- rnorm(10, mean=rep(1:5, each=2), sd=0.4)
#' y <- rnorm(10, mean=rep(c(1,2), each=5), sd=0.4)
#' dataFrame <- data.frame(x=x, y=y, row.names=c(1:10))
#' #calculate Euclidian distance
#' distxy <- dist(dataFrame)
#' #hierachical clustering "complete" linkage by default
#' hc <- hclust(distxy)
#'
#' #sort dendrogram
#' dd <- dendsort(as.dendrogram(hc))
#' hc_sorted  <- as.hclust(dd)
#'
#' #sort in reverse, you can also pass hclust object
#' plot(dendsort(hc, isReverse=TRUE))
#'
#' #sort by average distance
#' plot(dendsort(hc, type="average"))
#'
#' #plot the result
#' par(mfrow = c(1, 3), mai=c(0.8,0.8,2,0.8))
#' plot(x, y, col="gray", pch=19, cex=2)
#' text(x, y, labels=as.character(1:10), cex=0.9)
#' plot(hc,main="before sorting", xlab="", sub="")
#' plot(hc_sorted, main="after sorting", xlab="", sub="")
#'

sort_smallest <- function(d) {
if(class(d)!="dendrogram"){stop("d variable must be a dendrogram")}

a <- attributes(d)
left <- d[[1]]
right <- d[[2]]

if (is.leaf(left) && is.leaf(right)) {
n <- d
attr(n,"min") <- a\$height
} else if (!is.leaf(left) && is.leaf(right)) {
n <- merge(sort_smallest(left),right,height=a\$height)
attr(n,"min") <- min(a\$height, attributes(n[[1]])\$min)
} else if (is.leaf(left) && !is.leaf(right)) {
n <- merge(sort_smallest(right), left, height=a\$height)
attr(n,"min") <- min(a\$height, attributes(n[[1]])\$min)
} else {
lft  <- sort_smallest(left)
rght <- sort_smallest(right)
left.min <- attributes(lft)\$min
right.min <- attributes(rght)\$min
if (left.min <= right.min) {
n <- merge(lft, rght, height=a\$height)
} else {
n <- merge(rght, lft, height=a\$height)
}
attr(n,"min") <- min(a\$height, left.min, right.min)
}
return(n)
}
```

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dendsort documentation built on April 20, 2021, 5:05 p.m.