I’ve looked at the documentation for Handling Mass Matrices for DifferentialEquations.jl. In the example was a singular matrix. I would like to know how to implement a state dependent mass matrix, where the matrix M in equation
Mu’ =f(u,p,t)
has the dependent variables in the matrix itself.

The image below is the equation I’m trying to replicate:

I’m trying to integrate from Matlab to Julia for this type of problem. I thought replacing the mass_matrix option with a function would work but it produces the method error MethodError: no method matching issingular(::typeof(function goes here))

We just need to clean up our documentation of DiffEqOperators to make it more clear how to define dependent DiffEqOperators, since that’s all it is (the mass matrix can be any DiffEqOperator)

Thank you for that. I’m still new to Julia, could you link me to the equation your code snippet is solving to help visualize it for me? I can try to figure out the syntax from there.

Has the solution to this problem updated? DifferentialEquations.jl documentation says that state dependent mass matrices are “not directly supported” and there is no documentation in DiffEqOperators.jl either. Would the current implementation support Complex variables? @ChrisRackauckas@Julius_Martensen