If switch is set to -yes, the friction coefficient for contact springs will be determined from the plasticity law angle of neighbouring elements. For a neighbouring group_materi_plasti_mohrcoul the friction coefficient will be set to with the friction angle in the mohr-coulomb law of the neighbouring elements. For a neighbouring group_materi_plasti_diprisco the friction coefficient will be set to a value depending on the parameter of that law.
If no neigbouring elements with appropriate material law are found, then f will be set to 0.2.
The index specifies the element_group, see element_group.