G = addgroup(G,GroupName,GroupContents)
G [ grouping ] - Grouping object.
GroupName [ char ] - Group name.
GroupContents [ char | cell | Inf ] - Names of shocks or measurement variables to be included in the new group; GroupContents can also be regular expressions; Inf the group will contain all shocks or measurement variables not included in any existing group.
G [ grouping ] - Grouping object with the new group.