[R-sig-ME] singular convergence warning

[Price, Emily]

Dear R mixed models users,

I'm running a Monte Carlo simulation with 16 cells using four loops to determine how sample size influences treatment effectiveness in single case design.  I'm running 1,000 replications for each cell so I have a total of 16,000 simulated datasets.  In 50 of the 16,000 datasets I'm getting the following warning message: In mer_finalize(ans) : singular convergence (7).  I would like to determine where the errors are occurring (i.e., which cells) so that I can do some follow up analyses but  I don't know  how to program a statement to tell me.  To let me know when each sample is finished within a cell I'm using the command:  cat("Iteration",i1,i2,i3,i4,t,"successful","\n") where i1, i2, i3, and i4 are the counters for each for loop and t is the value for the replication number within each cell.  Therefore, does anyone know how to use command cat to print the values of the specific cell when the warning message occurs? Or alternatively if there is a different way I would welcome that as well.  If you would like additional information about the code I can supply that as well.

Thanks!
Emily

Emily A. Price, PhD
Educational Research and Evaluation
Patton College of Education
Ohio University


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