MLE.function: no visible global function definition for ‘optim’
MLE.function: no visible global function definition for ‘pchisq’
OR.sar.log: no visible global function definition for ‘qnorm’
RD.sar: no visible global function definition for ‘qnorm’
RR.sar.log: no visible global function definition for ‘qnorm’
forestplot: no visible global function definition for ‘pdf’
forestplot: no visible global function definition for ‘par’
forestplot: no visible global function definition for ‘plot’
forestplot: no visible global function definition for ‘segments’
forestplot: no visible global function definition for ‘axis’
forestplot: no visible global function definition for ‘arrows’
forestplot: no visible global function definition for ‘abline’
forestplot: no visible global function definition for ‘dev.off’
inde.sampling.posterior: no visible global function definition for
  ‘rbeta’
logSarmanov.dens: no visible global function definition for ‘dbeta’
minlength.CI: no visible global function definition for ‘quantile’
multipletables_sar: no visible global function definition for
  ‘quantile’
multipletables_sar: no visible binding for global variable ‘quantile’
multipletables_sar: no visible binding for global variable ‘density’
multipletables_sar: no visible global function definition for ‘density’
overlapplot_multiple: no visible global function definition for
  ‘quantile’
overlapplot_multiple: no visible global function definition for ‘pdf’
overlapplot_multiple: no visible global function definition for ‘par’
overlapplot_multiple: no visible global function definition for ‘plot’
overlapplot_multiple: no visible global function definition for ‘axis’
overlapplot_multiple: no visible global function definition for
  ‘abline’
overlapplot_multiple: no visible global function definition for
  ‘points’
overlapplot_multiple: no visible global function definition for
  ‘legend’
overlapplot_multiple: no visible global function definition for
  ‘dev.off’
overlapplot_single: no visible global function definition for
  ‘quantile’
overlapplot_single: no visible global function definition for ‘pdf’
overlapplot_single: no visible global function definition for ‘plot’
overlapplot_single: no visible global function definition for ‘points’
overlapplot_single: no visible global function definition for ‘abline’
overlapplot_single: no visible global function definition for ‘axis’
overlapplot_single: no visible global function definition for ‘legend’
overlapplot_single: no visible global function definition for ‘dev.off’
sideplot_multiple: no visible global function definition for ‘pdf’
sideplot_multiple: no visible global function definition for ‘dev.new’
sideplot_multiple: no visible global function definition for ‘par’
sideplot_multiple: no visible global function definition for ‘quantile’
sideplot_multiple: no visible global function definition for ‘plot’
sideplot_multiple: no visible global function definition for ‘axis’
sideplot_multiple: no visible global function definition for ‘points’
sideplot_multiple: no visible global function definition for ‘abline’
sideplot_multiple: no visible global function definition for ‘legend’
sideplot_multiple: no visible global function definition for ‘dev.off’
sideplot_single: no visible global function definition for ‘pdf’
sideplot_single: no visible global function definition for ‘par’
sideplot_single: no visible global function definition for ‘quantile’
sideplot_single: no visible global function definition for ‘plot’
sideplot_single: no visible global function definition for ‘abline’
sideplot_single: no visible global function definition for ‘axis’
sideplot_single: no visible global function definition for ‘legend’
sideplot_single: no visible global function definition for ‘dev.off’
singletable: no visible global function definition for ‘quantile’
singletable: no visible binding for global variable ‘density’
study_specifc: no visible binding for global variable ‘quantile’
summary_single_sampling: no visible global function definition for
  ‘median’
summary_single_sampling: no visible global function definition for
  ‘quantile’
Undefined global functions or variables:
  abline arrows axis dbeta density dev.new dev.off legend median optim
  par pchisq pdf plot points qnorm quantile rbeta segments
Consider adding
  importFrom("grDevices", "dev.new", "dev.off", "pdf")
  importFrom("graphics", "abline", "arrows", "axis", "legend", "par",
             "plot", "points", "segments")
  importFrom("stats", "dbeta", "density", "median", "optim", "pchisq",
             "qnorm", "quantile", "rbeta")
to your NAMESPACE file.