Dear all,
I have been running single season model for 40 different trails and included canopy cover % as one of the covariate. When I modeled site occupancy changes with canopy cover in the results I got a warning message. ********************** WARNING ***************************
Variance-covariance matrix has not been computed successfully.
Ignore matrix values in the below output.
--------------------------------------------------------------
In contrast when I normalized canopy% covariates this warning didn’t appear for any of the results. Is it mandatory that one should always normalize the covariates before saving for the analysis?
I also have 1, O (presence or absence) data for other covariates like disturbance, water body & grass marsh. Here the problem is slightly different I also get an other warning message along with it:
Numerical convergence may not have been reached.
Parameter estimates converged to approximately
2.69 significant digits.
Moreover in some case there is no warning message however the estimated occupancy is 1.000, which eventually becomes the best in selected models.
What’s causing the problem?
Can anyone clarify it for me?
Thanks in advance,
Deepak