A robust filter in stock networks analysis

► In practice, it is very often that a network between stocks contains more than one minimal spanning tree. ► A necessary and sufficient condition for the uniqueness of the minimal spanning tree is presented. ► If the minimal spanning tree is not unique, its use to filter important information might be misleading. Then it is non-robust. ► We propose then to use the forest of all minimal spanning trees as a robust filter. ► For practical purpose, an algorithm to construct that forest is developed.