a2sf: no visible global function definition for 'stepfun'
buildS: no visible global function definition for 'optimize'
plot.AssetPricing: no visible global function definition for 'plot'
plot.flap: no visible global function definition for 'par'
plot.flap : startPlot: no visible global function definition for 'plot'
plot.flap : startPlot: no visible global function definition for 'axis'
plot.flap: no visible global function definition for 'plot'
plot.flap: no visible global function definition for 'text'
plot.flap: no visible global function definition for 'mtext'
plot.flap: no visible global function definition for 'dev.interactive'
plot.stepfun: no visible global function definition for 'par'
plot.stepfun: no visible global function definition for 'is.stepfun'
plot.stepfun: no visible global function definition for 'ecdf'
plot.stepfun: no visible global function definition for 'knots'
plot.stepfun: no visible global function definition for 'median'
plot.stepfun: no visible global function definition for 'segments'
plot.stepfun: no visible global function definition for 'plot'
plot.stepfun: no visible global function definition for 'points'
putAway : <anonymous>: no visible global function definition for
  'approxfun'
putAway : <anonymous>: no visible global function definition for
  'splinefun'
turnPts: no visible global function definition for 'deriv'
vsolve: no visible global function definition for 'deriv3'
xsolve.cont: no visible global function definition for 'deriv3'
Undefined global functions or variables:
  approxfun axis deriv deriv3 dev.interactive ecdf is.stepfun knots
  median mtext optimize par plot points segments splinefun stepfun text
Consider adding
  importFrom("grDevices", "dev.interactive")
  importFrom("graphics", "axis", "mtext", "par", "plot", "points",
             "segments", "text")
  importFrom("stats", "approxfun", "deriv", "deriv3", "ecdf",
             "is.stepfun", "knots", "median", "optimize", "splinefun",
             "stepfun")
to your NAMESPACE file.