Error(s) in re-building vignettes:
--- re-building ‘Using_predictInterval.Rmd’ using rmarkdown
Loading required package: arm
Loading required package: MASS
Loading required package: Matrix
Loading required package: lme4

arm (Version 1.10-1, built: 2018-4-12)

Working directory is /data/gannet/ripley/R/packages/tests-clang/merTools.Rcheck/vign_test/merTools/vignettes

Loading required package: dplyr

Attaching package: 'dplyr'

The following object is masked from 'package:MASS':

    select

The following objects are masked from 'package:stats':

    filter, lag

The following objects are masked from 'package:base':

    intersect, setdiff, setequal, union

Loading required package: Rcpp
rstanarm (Version 2.18.2, packaged: 2018-11-08 22:19:38 UTC)
- Do not expect the default priors to remain the same in future rstanarm versions.
Thus, R scripts should specify priors explicitly, even if they are just the defaults.
- For execution on a local, multicore CPU with excess RAM we recommend calling
options(mc.cores = parallel::detectCores())
- Plotting theme set to bayesplot::theme_default().
--- finished re-building ‘Using_predictInterval.Rmd’

--- re-building ‘imputation.Rmd’ using rmarkdown
Loading required package: arm
Loading required package: MASS
Loading required package: Matrix
Loading required package: lme4

arm (Version 1.10-1, built: 2018-4-12)

Working directory is /data/gannet/ripley/R/packages/tests-clang/merTools.Rcheck/vign_test/merTools/vignettes

Loading required package: dplyr

Attaching package: 'dplyr'

The following object is masked from 'package:MASS':

    select

The following objects are masked from 'package:stats':

    filter, lag

The following objects are masked from 'package:base':

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Loading required package: Rcpp
## 
## Amelia II: Multiple Imputation
## (Version 1.7.5, built: 2018-05-07)
## Copyright (C) 2005-2019 James Honaker, Gary King and Matthew Blackwell
## Refer to http://gking.harvard.edu/amelia/ for more information
## 
--- finished re-building ‘imputation.Rmd’

--- re-building ‘merToolsIntro.Rmd’ using rmarkdown
Loading required package: arm
Loading required package: MASS
Loading required package: Matrix
Loading required package: lme4

arm (Version 1.10-1, built: 2018-4-12)

Working directory is /data/gannet/ripley/R/packages/tests-clang/merTools.Rcheck/vign_test/merTools/vignettes

Loading required package: dplyr

Attaching package: 'dplyr'

The following object is masked from 'package:MASS':

    select

The following objects are masked from 'package:stats':

    filter, lag

The following objects are masked from 'package:base':

    intersect, setdiff, setequal, union

Quitting from lines 357-368 (merToolsIntro.Rmd) 
Error: processing vignette 'merToolsIntro.Rmd' failed with diagnostics:
sigma must be a symmetric matrix
--- failed re-building ‘merToolsIntro.Rmd’

SUMMARY: processing the following file failed:
  ‘merToolsIntro.Rmd’

Error: Vignette re-building failed.
Execution halted