Method that runs the agnes algorithm using the manhattan metric to make an external or internal validation of the cluster
agnes_manhattan_method(dt, clusters, metric)
dt: matrix or data frame with the set of values to be applied to the algorithm.clusters: is an integer that indexes the number of clusters we want to create.metric: is a characters vector with the metrics avalaible in the package. The metrics implemented are: entropy, variation_information, precision,recall,f_measure,fowlkes_mallows_index,connectivity,dunn, silhouette.returns a list with both the internal and external evaluation of the grouping.