Error(s) in re-building vignettes:
  ...
--- re-building ‘Titanic_example.Rmd’ using rmarkdown
── Attaching packages ─────────────────────────────────────── tidyverse 1.3.1 ──
✔ ggplot2 3.3.3     ✔ purrr   0.3.4
✔ tibble  3.1.2     ✔ dplyr   1.0.6
✔ tidyr   1.1.3     ✔ stringr 1.4.0
✔ readr   1.4.0     ✔ forcats 0.5.1
── Conflicts ────────────────────────────────────────── tidyverse_conflicts() ──
✖ dplyr::filter() masks stats::filter()
✖ dplyr::lag()    masks stats::lag()
Loading required package: lattice

Attaching package: 'caret'

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

    lift

Loading required package: grid
Loading required package: mvtnorm
Loading required package: modeltools
Loading required package: stats4
Loading required package: strucchange
Loading required package: zoo

Attaching package: 'zoo'

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

    as.Date, as.Date.numeric

Loading required package: sandwich

Attaching package: 'strucchange'

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

    boundary

Loading required package: libcoin

Attaching package: 'partykit'

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

    cforest, ctree, ctree_control, edge_simple, mob, mob_control,
    node_barplot, node_bivplot, node_boxplot, node_inner, node_surv,
    node_terminal, varimp

Type 'citation("pROC")' for a citation.

Attaching package: 'pROC'

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

    cov, smooth, var


Attaching package: 'measures'

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

    MAE, RMSE


Attaching package: 'varImp'

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

    varImp


Attaching package: 'pdp'

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

    partial


Attaching package: 'vip'

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

    vi

Quitting from lines 82-83 (Titanic_example.Rmd) 
Error: processing vignette 'Titanic_example.Rmd' failed with diagnostics:
'x' contains missing values
--- failed re-building ‘Titanic_example.Rmd’

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

Error: Vignette re-building failed.
Execution halted