Covariance between know predictors and simulated predictors

[hallegue]

When simulating predictors, squidSim allows to specify the covariance matrix between all these predictors. squidSim also allows to input the user data. However, the covariance between simulated and know predictors is not possible. This could be a very useful feature.

[joelpick]

This can be done through the model argument, as you can make a new variable that is dependent on a simulated or known predictor. This is a bit cumbersome, but I don't think it would be easy to implement otherwise