Slate (writing) Slate (writing) A slate is a thin piece of hard flat material, such as the rock also called slate, that is used as a medium for writing. The rock is “a metamorphic rock created by the recrystallization of the minerals in shale from clay to parallel-aligned, flat, flake-like minerals such as mica”. The writing slate consisted of a piece of slate, typically either 4x6 inches or 7x10 inches, encased in a wooden frame. A precise date range for writing slates of this type has not been established. Usually, a piece of cloth or slate sponge was used to clean it
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