Error(s) in re-building vignettes:
--- re-building ‘exampleBackShift.Rmd’ using rmarkdown
Warning in engine$weave(file, quiet = quiet, encoding = enc) :
  Pandoc (>= 1.12.3) not available. Falling back to R Markdown v1.
Loading required package: backShift
Loading required package: ggplot2
Loading required package: fields
Loading required package: spam
Loading required package: dotCall64
Loading required package: grid
Spam version 2.7-0 (2021-06-25) is loaded.
Type 'help( Spam)' or 'demo( spam)' for a short introduction 
and overview of this package.
Help for individual functions is also obtained by adding the
suffix '.spam' to the function name, e.g. 'help( chol.spam)'.

Attaching package: 'spam'

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

    backsolve, forwardsolve

Loading required package: viridis
Loading required package: viridisLite
See https://github.com/NCAR/Fields for
 an extensive vignette, other supplements and source code 
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  no font could be found for family "Arial"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  no font could be found for family "Arial"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  no font could be found for family "Arial"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  no font could be found for family "Arial"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  no font could be found for family "Arial"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  no font could be found for family "Arial"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  no font could be found for family "Arial"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  no font could be found for family "Arial"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  no font could be found for family "Arial"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
Warning in doTryCatch(return(expr), name, parentenv, handler) :
  font "Times-Roman" could not be found for family "serif"
No id variables; using all as measure variables
Quitting from lines 257-258 (exampleBackShift.Rmd) 
Error: processing vignette 'exampleBackShift.Rmd' failed with diagnostics:
polygon edge not found
--- failed re-building ‘exampleBackShift.Rmd’

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

Error: Vignette re-building failed.
Execution halted