lines.prc: no visible global function definition for 'plot'
lines.quad: no visible global function definition for 'plot'
plot.prc: no visible global function definition for 'coef'
plot.prc: no visible global function definition for 'plot'
plot.prc: no visible global function definition for 'lines'
plot.prc: no visible global function definition for 'points'
plot.prc: no visible global function definition for 'abline'
plot.quad: no visible global function definition for 'coef'
plot.quad: no visible global function definition for 'plot'
plot.quad: no visible global function definition for 'lines'
plot.quad: no visible global function definition for 'points'
prc: no visible global function definition for 'as.formula'
prc: no visible global function definition for 'coef'
prc: no visible global function definition for 'optim'
prc: no visible global function definition for 'optimize'
prcsp: no visible global function definition for 'coef'
prcsp: no visible global function definition for 'plot'
prcsp: no visible global function definition for 'abline'
prcsp: no visible global function definition for 'title'
prcsp: no visible global function definition for 'lm.fit'
prcsp: no visible global function definition for 'points'
prcsp: no visible global function definition for 'lines'
prcsp: no visible global function definition for 'par'
prcsp: no visible global function definition for 'optim'
prcsp : <anonymous>: no visible global function definition for 'dbeta'
prcsp: no visible global function definition for 'dbeta'
prcsp : debug.1: no visible global function definition for 'dbeta'
prcsp: no visible global function definition for 'nlminb'
prcsp: no visible global function definition for 'optimize'
predict.prc: no visible global function definition for 'coef'
quadratic.eiv: no visible global function definition for 'as.formula'
quadratic.eiv: no visible global function definition for 'coef'
quadratic.eiv: no visible global function definition for 'optim'
quadratic.eiv: no visible global function definition for 'optimize'
quadratic.eiv.sp: no visible global function definition for 'coef'
quadratic.eiv.sp: no visible global function definition for 'plot'
quadratic.eiv.sp: no visible global function definition for 'abline'
quadratic.eiv.sp: no visible global function definition for 'lm.fit'
quadratic.eiv.sp: no visible global function definition for 'points'
quadratic.eiv.sp: no visible global function definition for 'lines'
quadratic.eiv.sp: no visible global function definition for 'optim'
Undefined global functions or variables:
  abline as.formula coef dbeta lines lm.fit nlminb optim optimize par
  plot points title
Consider adding
  importFrom("graphics", "abline", "lines", "par", "plot", "points",
             "title")
  importFrom("stats", "as.formula", "coef", "dbeta", "lm.fit", "nlminb",
             "optim", "optimize")
to your NAMESPACE file.