r cmd check undefined global functions or variables 

参考  https://github.com/jennybc/googlesheets/blob/master/R/googlesheets.R

可在包的顶层文件，加上这一句

#' Your software package

#'

#' Your software package can do  something. 

#'

#' @docType package

#' @name YourPackageName

#' @rdname YourPackageNmae-package

#'

#' @author Cliff(  yourname@@example.com)

#'

NULL

if (getRversion()>="2.15.1") utils::globalVariables(c("YourGlobalVariable1","YourGlobalVariable2"))