I am trying to model a condition like: (x = 2$(y gt 1.5) + 0$(y le 1.5)), but there is an error message

 Endogenous $-control operations not allowed
 **** The following DNLP errors were detected in model opt:
 ****  52 equation equation2 .. VAR $-control.

You cannot use variables in a $ condition. The dollar condition must depend on data only.

When you try to do this with a NLP, it often means that you have a discrete aspect to their model that will require the introduction of binary variables – making the model type an MINLP (mixed integer nonlinear program) that needs to be solved with a solver like DICOPT or SBB. If you browse our model library, you'll find examples of MINLP models that might help.