So apologies if this sounds really basic, but I'm very new to meta-analysis, and this is my first ever time conducting one and using this software. I just wonder if someone could please guide me step-by-step in the most simplistic terms on how to actually include covariates? I would like to include age, gender, etc, but when I try to do this, I get the error 'gsl: lu.c:266: ERROR: matrix is singular gsl: lu.c:266: ERROR: matrix is singular Default GSL error handler invoked. gsl: lu.c:266: ERROR: matrix is singular gsl: lu.c:266: ERROR: matrix is singular gsl: lu.c:266: ERROR: matrix is singular' - All help is appreciated!

Hello, 

The covariables had to be a added in the paramters of the Mean analysis. If you get "singular matrix" you should review the design matirx you are introducing. How many covariables and which ones are you using?

Kind regards, 
Lydia

Hello, I've also encountered the same problem and would like to know how you solved it? If you could share the solution, I would be very grateful!