CHMsmoothing: no visible global function definition for ‘as’
CHMsmoothing: no visible binding for global variable ‘median’
FindTreesCHM: no visible global function definition for ‘as’
ForestCAS: no visible global function definition for ‘as’
ForestCAS: no visible global function definition for ‘na.omit’
ForestCAS: no visible global function definition for ‘slot’
ForestCAS : <anonymous>: no visible global function definition for
  ‘slot’
ForestCAS: no visible global function definition for ‘flush.console’
ForestCAS: no visible global function definition for ‘slot<-’
ForestCAS: no visible binding for global variable ‘slot’
LASmetrics: no visible global function definition for ‘median’
LASmetrics: no visible global function definition for ‘sd’
LASmetrics: no visible global function definition for ‘var’
LASmetrics: no visible global function definition for ‘quantile’
chullLiDAR2D: no visible global function definition for ‘chull’
chullLiDAR2D: no visible global function definition for ‘flush.console’
chullLiDAR2D: no visible global function definition for ‘slot’
chullLiDAR2D: no visible global function definition for ‘slot<-’
chullLiDAR2D: no visible binding for global variable ‘slot’
chullLiDAR3D: no visible global function definition for ‘flush.console’
rMetrics: no visible global function definition for ‘flush.console’
rMetrics: no visible global function definition for ‘median’
rMetrics: no visible global function definition for ‘var’
rMetrics: no visible global function definition for ‘sd’
rMetrics: no visible global function definition for ‘quantile’
readLAS: no visible global function definition for ‘?’
Undefined global functions or variables:
  ? as chull flush.console median na.omit quantile sd slot slot<- var
Consider adding
  importFrom("grDevices", "chull")
  importFrom("methods", "as", "slot", "slot<-")
  importFrom("stats", "median", "na.omit", "quantile", "sd", "var")
  importFrom("utils", "?", "flush.console")
to your NAMESPACE file (and ensure that your DESCRIPTION Imports field
contains 'methods').