Editing Distance matrix (section)

==== Hierarchical clustering ====
A distance matrix is necessary for traditional [[hierarchical clustering]] algorithms which are often heuristic methods employed in biological sciences such as phylogeny reconstruction. When implementing any of the hierarchical clustering algorithms in data mining, the distance matrix will contain all pair-wise distances between every point and then will begin to create clusters between two different points or clusters based entirely on distances from the distance matrix.

If N be the number of points, the complexity of hierarchical clustering is:

* Time complexity is <math>O(N^3)</math> due to the repetitive calculations done after every cluster to update the distance matrix
* Space complexity is <math>O(N^2)</math>