Abscissa and ordinate Abscissa and ordinate In mathematics, the abscissa (; plural "abscissae" or "abscissæ" or "abscissas") and the ordinate are respectively the first and second coordinate of a point in a coordinate system. The abscissa of a point is the signed measure of its projection on the primary axis, whose absolute value is the distance between the projection and the origin of the axis, and whose sign is given by the location on the projection relative to the origin (before: negative; after: positive). The ordinate of a point is the signed measure of its projection on the secondary axis, whose absolute value
Spectral abscissa Spectral abscissa In mathematics, the spectral abscissa of a matrix or a bounded linear operator is the supremum among the real part of the elements in its spectrum, sometimes denoted as formula_1 Let λ, ..., λ be the (real or complex) eigenvalues of a matrix "A" ∈ C. Then its spectral abscissa is defined as: For example, if the set of eigenvalues were = {1+3i,2+3i,4-2i}, then the Spectral abscissa in this case would be 4. It is often used as a measure of stability in control theory, where a continuous system is stable if all its eigenvalues are located in