COGravity: no visible global function definition for 'sd'
ClassStat: no visible global function definition for 'na.omit'
ClassStat: no visible global function definition for 'sd'
ConnCompLabel: no visible global function definition for 'setValues'
ImageDiff: no visible global function definition for 'terrain.colors'
ImageDiff: no visible global function definition for 'image'
PatchStat: no visible global function definition for 'na.omit'
Scalebar: no visible global function definition for 'rect'
Scalebar: no visible global function definition for 'segments'
Scalebar: no visible global function definition for 'text'
SigDiff: no visible global function definition for 'pnorm'
SigDiff: no visible global function definition for 'setValues'
ZonalStat: no visible global function definition for 'na.omit'
ZonalStat: no visible global function definition for 'quantile'
asc.from.raster: no visible global function definition for 'getValues'
asc2dataframe: no visible global function definition for 'na.omit'
aspect: no visible global function definition for 'setValues'
compare.matrix: no visible global function definition for 'aggregate'
compare.matrix: no visible global function definition for 'image'
compare.matrix: no visible global function definition for 'heat.colors'
compare.matrix: no visible global function definition for 'contour'
grid.area: no visible global function definition for 'setValues'
grid.perimeter: no visible global function definition for 'setValues'
image.asc: no visible global function definition for 'gray'
image.asc: no visible global function definition for 'image'
image.asc: no visible global function definition for 'rainbow'
lcmw: no visible global function definition for 'na.omit'
lcmw: no visible global function definition for 'setValues'
legend.gradient: no visible global function definition for
  'heat.colors'
legend.gradient: no visible global function definition for 'polygon'
legend.gradient: no visible global function definition for 'text'
quick.map: no visible global function definition for 'heat.colors'
quick.map: no visible global function definition for 'image'
raster.from.asc: no visible global function definition for 'raster'
raster.from.asc: no visible global function definition for
  'projection<-'
raster.from.asc: no visible global function definition for 'setValues'
slope: no visible global function definition for 'setValues'
sp.from.asc: no visible global function definition for 'CRS'
sp.from.asc: no visible global function definition for 'GridTopology'
sp.from.asc: no visible global function definition for
  'SpatialGridDataFrame'
Undefined global functions or variables:
  CRS GridTopology SpatialGridDataFrame aggregate contour getValues
  gray heat.colors image na.omit pnorm polygon projection<- quantile
  rainbow raster rect sd segments setValues terrain.colors text
Consider adding
  importFrom("grDevices", "gray", "heat.colors", "rainbow",
             "terrain.colors")
  importFrom("graphics", "contour", "image", "polygon", "rect",
             "segments", "text")
  importFrom("stats", "aggregate", "na.omit", "pnorm", "quantile", "sd")
to your NAMESPACE file.