Extract cluster membership vector from one solutions matrix row
get_clusters.RdThis function takes in a single row of a solutions matrix and returns a
vector containing the cluster assignments for each observation. It is
similar to get_cluster_df(), which takes a solutions matrix with only one
row and returns a dataframe with two columns: "cluster" and "subjectkey"
'(the UID of the observation) and get_cluster_solutions(), which takes a
solutions matrix with any number of rows and returns a dataframe indicating
the cluster assignments for each of those rows.