how to convert a data.frame to tree structure object such as dendrogram

Question

I have a data.frame object. For a simple example:

> data.frame(x=c(\'A\',\'A\',\'B\',\'B\',\'B\'), y=c(\'Ab\',\'Ac\',\'Ba\', \'Ba\',\'Bd\'), z=c(\'Abb\',\         


        

Answer 1

I don't know much about the internal structure of dendrograms in R, but the following code will create a nested list structure that has the hierarchy that I think you look for:

stree = function(x,level=0) {
#x is a string vector
#resultis a hierarchical structure of lists (that contains lists, etc.)
#the names of the lists are the node values.

level = level+1
if (length(x)==1) {
    result = list()
    result[[substring(x[1],level)]]=list()
    return(result)
}
result=list()
this.level = substring(x,level,level)
next.levels = unique(this.level)
for (p in next.levels) {
    if (p=="") {
        result$p = list()
    } else {
        ids = which(this.level==p)
        result[[p]] = stree(x[ids],level)
    }
}
result
}

it operates on a vector of strings. so in case of your dataframe you'd need to call stree(as.character(df[,3]))

Hope this helps.