by jpfeifer » Sun Jul 07, 2013 7:08 pm
The reason is numerical. A computer always has to make a decision what to take as 0, even if it is not exactly 0. If you look into model_diagnostics, you will see that some choices have to be made what to count as singular as opposed to close to singular. The output of model_diagnostics should thus be seen as providing guidelines what to look at. You should not interpret it as a strict analytical statement.