I've been running basic, univariate twin models over the last week and have had no troubles, but today (March 14) I began receiving the following error in response to this code. The code is nearly identical to the code used at the Twin Workshop, with the exception of different variables and had worked fine up until now even with the new variables. Any ideas of what might be causing this (it seems like a technical issue rather than a modeling issue, but I may be wrong)?
+ mxAlgebra( MZ.objective + DZ.objective, name="-2sumll" ),
Error: The name '-2sumll' is illegal because it contains the '-' character.