Question 4 [10 pts] - Clustering Suppose that we have four observations, for which we compute a dissimilarity matrix, given by 0 0.3 0.4 0.7 0.3 0 0.5 0.8 0.4 0.5 0 0.45 0.7 0.8 0.45 0 For instance, the dissimilarity between the first and second observations is 0.3, and the dissimilarity between the second and fourth observations is 0.8. On the basis of this dissimi- larity matrix, we could sketch the dendrogram in R that results from hierarchical clustering for these four observations using complete linkage. The dendrogram plot is given in the following d = as . dist (matrix(c(0, 0.3, 0.4, 0.7, 0.3, 0, 0.5, 0.8, 0.4, 0.5, 0.0, 0.45, 0.7, 0.8, 0.45, 0.0), now = 4)) plot (helust (d, method = "complete")) Cluster Dendrogram 0.3 0.4 0.5 0.6 0.7 0.8 Height d hclust (*, "complete") (a) [3 pts] From the dendrogram, how many steps do we need to get this sketch? What is the first step doing? Why the height of cluster of observations (1,2) is 0.3 in the dendrogram? (b) [2 pts] Suppose that we cut the dendrogram obtained in (a) such that two clusters result. List the observations in each cluster. (c) [2 pts ] Learn from the given R code and dendrogram plot, now coudld you produce the dendrogram using single linkage. Submit your dendrogram plot as the solution. For the submitted plot, you could either sketch it or get the plot from R. (d) [2 pts] For the dendrogram you obtained in (c), if you cut at height=0.35, how many clusters do you have? List the observations in each cluster. (e) [1 pt] compare dendrogram plots using complete and single linkage, what is the disad- vantage of hierarchical clustering