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How do you find P distance?
p-distance This distance is merely the proportion (p) of nucleotide sites at which the two sequences compared are different. This is obtained by dividing the number of nucleotide differences (nd) by the total number of nucleotides compared (n). Thus, p = nd/n.
Is PAM and K medoids same?
The difference is in new medoid selection (per iteration): K-medoids selects object that is closest to the medoid as a next medoid. PAM tries out all of the objects in the cluster as a new medoid that will lead to lower SSE.
How to cluster given pairwise distances with Mij?
I have calculated the pairwise distances of all possible pairs. The distances are stored in a n*n matrix M, with Mij being the distance between obji and objj. Then it is natural to see M is a symmetric matrix. Now I wish to perform unsupervised clustering to these objects.
What are the two types of clustering algorithms?
It has two types: Agglomerative or “bottom up” approach: each observation starts in its own cluster, and pairs of clusters are merged as one moves up the hierarchy. Divisive or “top down” approach: all observations start in one cluster, and splits are performed recursively as one moves down the hierarchy.
How to calculate the number of clusters in a data set?
In the meantime, however, a couple of recent approaches to the problem are: Estimating the number of clusters in a data set via the gap statistic by Tibshirani, Walther and Hastie, which compares the change in within-cluster dispersion with the number of clusters against the expected change for an appropriate reference null distribution.
Which is more common, clustering or cross validated?
Clustering methods that require the number of clusters a priori are much more common than those that try to estimate the number of clusters. You might get better answers at Cross Validated. In the meantime, however, a couple of recent approaches to the problem are: