[R-sig-ME] lmer warning on certain OS

[Laura Chihara]

I'm teaching an undergraduate statistics class and was preparing to do 
some simple examples which ran fine the last time I taught. But this 
time, I am getting warning messages (though the summary output looks OK).

These warnings occur on a Dell desktop running Windows 10 as well as a 
Windows Surface 7. I also ran this on RStudio running on a college 
server which is a Unix server (Ubuntu 16.04.6 LTS) and saw the warning. 
However, the warning message does not occur on an Apple machine nor on 
RStudio-Cloud (https://rstudio.cloud).

(I am running the most recent version of R, RStudio and lme4).

#-----------------------------
# R Script attached has the following

library(lme4)
library(nlme)
lmer(height ~ age + (age | Subject), Oxboys) #warning

mean(Oxboys$age)
Oxboys$age2 <- Oxboys$age - mean(Oxboys$age)
lmer(height ~ age2 + (age2|Subject), Oxboys)  #no warning


lmer(distance ~ age + (age |Subject), Orthodont) #warning

#But a more complicated mode:
lmer(distance ~ age*Sex + (age|Subject), Orthodont)
#--------------------------------------------------------------------------------------

#Warning:

Warning message: In checkConv(attr(opt, "derivs"), opt$par, ctrl = 
control$checkConv, : Model failed to converge with max|grad| = 0.110724 
(tol = 0.002, component 1)

#session info

> sessionInfo() R version 3.6.3 (2020-02-29) Platform: 
x86_64-w64-mingw32/x64 (64-bit) Running under: Windows 10 x64 (build 
18362) Matrix products: default Random number generation: RNG: 
Mersenne-Twister Normal: Inversion Sample: Rounding locale: [1] 
LC_COLLATE=English_United States.1252 LC_CTYPE=English_United 
States.1252 [3] LC_MONETARY=English_United States.1252 LC_NUMERIC=C [5] 
LC_TIME=English_United States.1252 attached base packages: [1] stats 
graphics grDevices utils datasets methods base other attached packages: 
[1] nlme_3.1-144 lme4_1.1-21 Matrix_1.2-18 loaded via a namespace (and 
not attached): [1] minqa_1.2.4 MASS_7.3-51.5 compiler_3.6.3 tools_3.6.3 
Rcpp_1.0.4 [6] splines_3.6.3 grid_3.6.3 nloptr_1.2.2.1 boot_1.3-24 
lattice_0.20-38

-- 

####################################################
Laura Chihara
Prof. of Mathematics and Statistics
Dept. of Mathematics and Statistics
One North College St.
Carleton College
Northfield Mn 55057


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