assignments: no visible global function definition for 'combn'
assignments: no visible global function definition for 'write.table'
assignments: no visible global function definition for 'read.table'
assignments: no visible global function definition for 'memory.limit'
distribution.random: no visible global function definition for
  'read.table'
distribution.random: no visible global function definition for
  'write.table'
distribution.systematic: no visible global function definition for
  'read.table'
distribution.systematic: no visible global function definition for
  'combn'
distribution.systematic: no visible global function definition for
  'write.table'
graph1: no visible global function definition for 'read.table'
graph1: no visible global function definition for 'plot'
graph1: no visible global function definition for 'points'
graph1: no visible global function definition for 'lines'
graph1: no visible global function definition for 'legend'
graph1: no visible global function definition for 'locator'
graph1: no visible global function definition for 'mtext'
graph1: no visible global function definition for 'par'
graph1: no visible global function definition for 'title'
observed: no visible global function definition for 'read.table'
pvalue.random: no visible global function definition for 'read.table'
pvalue.random: no visible global function definition for 'write.table'
pvalue.systematic: no visible global function definition for
  'read.table'
pvalue.systematic: no visible global function definition for 'combn'
pvalue.systematic: no visible global function definition for
  'write.table'
quantity: no visible global function definition for 'combn'
quantity: no visible global function definition for 'write.table'
quantity: no visible global function definition for 'read.table'
selectdesign: no visible global function definition for 'read.table'
Undefined global functions or variables:
  combn legend lines locator memory.limit mtext par plot points
  read.table title write.table
Consider adding
  importFrom("graphics", "legend", "lines", "locator", "mtext", "par",
             "plot", "points", "title")
  importFrom("utils", "combn", "memory.limit", "read.table",
             "write.table")
to your NAMESPACE file.