Idempotent matrix

In algebra, an idempotent matrix is a matrix which, when multiplied by itself, yields itself. That is, the matrix M is idempotent if and only if MM = M. For this product MM to be defined, M must necessarily be a square matrix. Viewed this way, idempotent matrices are idempotent elements of matrix rings. This video is targeted to blind users. Attribution: Article text available under CC-BY-SA Creative Commons image source in video