duane: no visible global function definition for 'optim'
duane.plot: no visible global function definition for 'plot'
duane.plot: no visible global function definition for 'lines'
duane.plot: no visible global function definition for 'legend'
duane.plot: no visible global function definition for 'title'
littlewood.verall: no visible global function definition for 'optim'
littlewood.verall.plot: no visible global function definition for
  'plot'
littlewood.verall.plot: no visible global function definition for
  'lines'
littlewood.verall.plot: no visible global function definition for
  'legend'
littlewood.verall.plot: no visible global function definition for
  'title'
moranda.geometric: no visible global function definition for 'optimize'
moranda.geometric.plot: no visible global function definition for
  'plot'
moranda.geometric.plot: no visible global function definition for
  'lines'
moranda.geometric.plot: no visible global function definition for
  'legend'
moranda.geometric.plot: no visible global function definition for
  'title'
musa.okumoto: no visible global function definition for 'optimize'
musa.okumoto.plot: no visible global function definition for 'plot'
musa.okumoto.plot: no visible global function definition for 'lines'
musa.okumoto.plot: no visible global function definition for 'legend'
musa.okumoto.plot: no visible global function definition for 'title'
rel.plot: no visible global function definition for 'plot'
rel.plot: no visible global function definition for 'lines'
rel.plot: no visible global function definition for 'segments'
rel.plot: no visible global function definition for 'legend'
rel.plot: no visible global function definition for 'title'
total.plot: no visible global function definition for 'plot'
total.plot: no visible global function definition for 'lines'
total.plot: no visible global function definition for 'legend'
total.plot: no visible global function definition for 'title'
Undefined global functions or variables:
  legend lines optim optimize plot segments title
Consider adding
  importFrom("graphics", "legend", "lines", "plot", "segments", "title")
  importFrom("stats", "optim", "optimize")
to your NAMESPACE file.