c1.n=function(data,s2,Mbar,N,param,B){
  data=as.name(data); N=N; s2=s2; B=B
  Mbar=Mbar; param=as.name(param)
  if(param=='total'){
    D=B^2/(4*N^2)
  } else {
    D=(B^2*Mbar^2)/4
  }
  n=ceiling((N*s2)/(N*D+s2))
  cat("","\n","Sample size estimation for 1 stage cluster design","\n","Data:",data,"\n",'Estimation for',param,'\n',
      "N =",N,"Required bound =",B,'\n',"Estimated variance =",s2,"\n","Estimated n =",n,"\n")
  results=list(data=data,N=N,s2=s2,B=B,D=D,n=n,param=param)
}
# to use the function with its call:
# c1.n(data,s2,Mbar,N,param,B)

# data: name of dataset, in quotes
# s2: s2r when M known, s2t when M unknown
# Mbar: either Mbar or mbar (single number)
# N: population size (single number)
# param: c('mean','total','proportion')
# B: desired bound