Separation occurs in binomial response models when a combination of the predictor variables perfectly predict a level of the response. In such a case the estimates of the coefficients for these variables diverge to (+/-)infinity, and the numerical algorithms typically fail. To anticipate such a problem, the fitting functions in spaMM try to check for separation by default, using the lpSolveAPI package which can also detect some borderline cases (“quasi-separation”). It this package is not available, spaMM tries to use the e1071 package (in a way which will not detect quasi-separation), except for large data sets where this may take time, in which case a message notifies this to the user. The threshold size of the data is set by spaMM.options(separation_max=<.>)