groc.default: no visible global function definition for
  'model.response'
groc.default: no visible global function definition for 'model.matrix'
groc.fit: no visible global function definition for 'fitted'
grocCrossval: no visible global function definition for 'model.frame'
grocCrossval: no visible global function definition for 'formula'
grocCrossval: no visible global function definition for
  'model.response'
grocCrossval: no visible global function definition for 'update'
grocCrossval: no visible binding for global variable 'median'
grocCrossval: no visible global function definition for 'fitted'
model.matrix.groc: no visible global function definition for
  'model.frame'
model.matrix.groc: no visible global function definition for 'terms'
plot.groc: no visible global function definition for 'qchisq'
plot.groc: no visible global function definition for 'residuals'
plot.groc: no visible global function definition for 'abline'
plot.groc: no visible global function definition for 'text'
plot.groc: no visible binding for global variable 'sd'
plot.groc: no visible global function definition for 'mahalanobis'
plot.groc: no visible global function definition for 'var'
plot.groc: no visible global function definition for 'par'
predict.groc: no visible binding for global variable 'na.pass'
predict.groc: no visible global function definition for 'model.matrix'
predict.groc: no visible global function definition for
  'delete.response'
predict.groc: no visible global function definition for 'terms'
predict.groc: no visible global function definition for 'model.frame'
predict.groc: no visible global function definition for
  '.checkMFClasses'
Undefined global functions or variables:
  .checkMFClasses abline delete.response fitted formula mahalanobis
  median model.frame model.matrix model.response na.pass par qchisq
  residuals sd terms text update var
Consider adding
  importFrom("graphics", "abline", "par", "text")
  importFrom("stats", ".checkMFClasses", "delete.response", "fitted",
             "formula", "mahalanobis", "median", "model.frame",
             "model.matrix", "model.response", "na.pass", "qchisq",
             "residuals", "sd", "terms", "update", "var")
to your NAMESPACE file.