Dear R-helpers, I'm analyzing a data with hierarchical linear model. I have one level 1 predictor and one level 2 predictor, which looks like below: fm1 <- lmer(y ~ 1 + x1 + x2 + x1:x2 + (1 + x1 | id.full)) where: y is the outcome variable. x1 is the level 1 predictor variable. x2 is the level 2 predictor variable. id.full is the conditioned variable. It runs beautifully when only x1 is centered (I subtracted the grand mean from each value). However, when I also centered x2 variable with the same procedure, it gives me the following error message: Warning message: In mer_finalize(ans) : singular convergence (7) I'd appreciate if someone could explain me what it means. One of the differences between "non-centered values" and "centered values" is that the "centered values" include negative values. Could it be the reason? If so, what shall I do? Thank you! Sachi
Dear R-helpers, I'm analyzing a data with hierarchical linear model. I have one level 1 predictor and one level 2 predictor, which looks like below: fm1 <- lmer(y ~ 1 + x1 + x2 + x1:x2 + (1 + x1 | id.full)) where: y is the outcome variable. x1 is the level 1 predictor variable. x2 is the level 2 predictor variable. id.full is the conditioned variable. It runs beautifully when only x1 is centered (I subtracted the mean from each value). However, when I also center x2 variable with the same procedure, it gives me the following error message: Warning message: In mer_finalize(ans) : singular convergence (7) I'd appreciate if someone could explain me what it means. One of the differences between "non-centered values" and "centered values" is that the "centered values" include negative values. Could it be the reason? If so, what shall I do? Thank you! [[alternative HTML version deleted]]