Slate Slate Slate is a fine-grained, foliated, homogeneous metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade regional metamorphism. It is the finest grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression. The foliation in slate is called "slaty cleavage". It is caused by strong compression causing fine grained clay flakes to regrow in planes perpendicular to the compression. When expertly "cut" by striking parallel to the foliation, with a specialized tool in the quarry, many slates
K-means++ the "k"-means++ initialization, the algorithm is guaranteed to find a solution that is O(log "k") competitive to the optimal "k"-means solution. To illustrate the potential of the "k"-means algorithm to perform arbitrarily poorly with respect to the objective function of minimizing the sum of squared distances of cluster points to the centroid of their assigned clusters, consider the example of four points in R that form an axis-aligned rectangle whose width is greater than its height. If "k" = 2 and the two initial cluster centers lie at the midpoints of the top and bottom line segments of the rectangle