F.3d.model.matrix: no visible global function definition for
  'model.matrix'
F.cjs.estim: no visible global function definition for
  'packageDescription'
F.cjs.estim: no visible global function definition for 'qnorm'
F.cjs.estim: no visible global function definition for 'predict'
F.cjs.estim: no visible global function definition for 'residuals'
F.cjs.gof: no visible global function definition for 'residuals'
F.cjs.gof: no visible global function definition for 'pchisq'
F.cjs.gof: no visible global function definition for 'pnorm'
F.cjs.gof: no visible global function definition for 'quantile'
F.cjs.simulate: no visible global function definition for 'rbinom'
F.cr.model.matrix: no visible global function definition for
  'as.formula'
F.huggins.estim: no visible global function definition for 'as.formula'
F.huggins.estim: no visible global function definition for
  'packageDescription'
F.step.cjs: no visible global function definition for 'formula'
ivar: no visible global function definition for 'model.matrix'
lines.cjs: no visible global function definition for 'matlines'
lines.cjs: no visible global function definition for 'lines'
plot.cjs: no visible global function definition for 'matplot'
plot.cjs: no visible global function definition for 'axis'
plot.nhat: no visible global function definition for 'plot'
plot.nhat: no visible global function definition for 'axis'
plot.nhat: no visible global function definition for 'lines'
plot.nhat: no visible global function definition for 'supsmu'
print.nhat: no visible global function definition for 'supsmu'
tvar: no visible global function definition for 'model.matrix'
Undefined global functions or variables:
  as.formula axis formula lines matlines matplot model.matrix
  packageDescription pchisq plot pnorm predict qnorm quantile rbinom
  residuals supsmu
Consider adding
  importFrom("graphics", "axis", "lines", "matlines", "matplot", "plot")
  importFrom("stats", "as.formula", "formula", "model.matrix", "pchisq",
             "pnorm", "predict", "qnorm", "quantile", "rbinom",
             "residuals", "supsmu")
  importFrom("utils", "packageDescription")
to your NAMESPACE file.