Error(s) in re-building vignettes:
  ...
--- re-building ‘lacunr-tutorial.Rmd’ using rmarkdown
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
Warning in hook_png(..., cmd = "pngquant", post_process = function(x) { :
  cannot find pngquant; please install and put it in PATH
[WARNING] Deprecated: --highlight-style. Use --syntax-highlighting instead.
--- finished re-building ‘lacunr-tutorial.Rmd’

--- re-building ‘quick-start.Rmd’ using rmarkdown
[WARNING] Deprecated: --highlight-style. Use --syntax-highlighting instead.
--- finished re-building ‘quick-start.Rmd’

--- re-building ‘working-with-lidR.Rmd’ using rmarkdown

Quitting from working-with-lidR.Rmd:55-60 [unnamed-chunk-5]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
<error/rlang_error>
Error in `[.data.table`:
! attempt access index 3/3 in VECTOR_ELT
---
Backtrace:
    ▆
 1. └─lidR::voxel_metrics(las_glassfire, ~list(N = length(Z)), res = 1)
 2.   ├─by[, `:=`(GRP, .GRP), by = c("Xgrid", "Ygrid", "Zgrid")]
 3.   └─data.table:::`[.data.table`(...)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Error: processing vignette 'working-with-lidR.Rmd' failed with diagnostics:
attempt access index 3/3 in VECTOR_ELT
--- failed re-building ‘working-with-lidR.Rmd’

SUMMARY: processing the following file failed:
  ‘working-with-lidR.Rmd’

Error: Vignette re-building failed.
Execution halted