estNodeRisk : node.sd.loss: no visible global function definition for
  'sd'
itree: no visible global function definition for 'model.extract'
itree.branch: no visible global function definition for 'dev.cur'
itree.exp: no visible global function definition for 'quantile'
itree.exp: no visible global function definition for 'approx'
path.itree: no visible global function definition for 'identify'
plot.itree: no visible global function definition for 'colors'
plot.itree: no visible global function definition for 'dev.cur'
plot.itree: no visible global function definition for 'lines'
plotcp: no visible global function definition for 'box'
plotcp: no visible global function definition for 'axis'
plotcp: no visible global function definition for 'segments'
plotcp: no visible global function definition for 'mtext'
plotcp: no visible global function definition for 'abline'
plotxvals: no visible global function definition for 'sd'
plotxvals: no visible binding for global variable 'sd'
plotxvals: no visible global function definition for 'par'
plotxvals: no visible global function definition for 'abline'
post.itree: no visible global function definition for 'postscript'
post.itree: no visible global function definition for 'par'
post.itree: no visible global function definition for 'dev.off'
post.itree: no visible global function definition for 'title'
predict.itree: no visible binding for global variable 'na.pass'
predict.itree: no visible global function definition for
  'delete.response'
predict.itree: no visible global function definition for
  '.checkMFClasses'
predict.itree: no visible global function definition for 'naresid'
print.itree: no visible global function definition for 'naprint'
printcp: no visible global function definition for 'naprint'
residuals.itree: no visible global function definition for
  'model.extract'
residuals.itree: no visible global function definition for 'naresid'
rpartco: no visible global function definition for 'dev.cur'
rsq.itree: no visible global function definition for 'par'
rsq.itree: no visible global function definition for 'legend'
rsq.itree: no visible global function definition for 'segments'
snip.itree.mouse: no visible global function definition for 'dev.cur'
snip.itree.mouse: no visible global function definition for 'identify'
snip.itree.mouse: no visible global function definition for 'lines'
summary.itree: no visible global function definition for 'naprint'
text.itree: no visible global function definition for 'par'
text.itree : oval: no visible global function definition for 'polygon'
text.itree : rectangle: no visible global function definition for
  'polygon'
xpred.itree: no visible global function definition for 'model.extract'
Undefined global functions or variables:
  .checkMFClasses abline approx axis box colors delete.response dev.cur
  dev.off identify legend lines model.extract mtext na.pass naprint
  naresid par polygon postscript quantile sd segments title
Consider adding
  importFrom("grDevices", "colors", "dev.cur", "dev.off", "postscript")
  importFrom("graphics", "abline", "axis", "box", "identify", "legend",
             "lines", "mtext", "par", "polygon", "segments", "title")
  importFrom("stats", ".checkMFClasses", "approx", "delete.response",
             "model.extract", "na.pass", "naprint", "naresid",
             "quantile", "sd")
to your NAMESPACE file.