R/t.sample.size.razao.R

In mleal93/t.sample: Sample Techiniques

#' @title Ratio Estimators Sample size calculation
#' 
#'
#' @description A function that returns the results from calculated estimated values for Ratio Estimators.
#' @import stats
#' @param data A data frame that contains x and y variables.
#' @param c.lev Confidence Level.
#' @param N Population size linked to x variable.
#' @param mu Population sugested mean.
#' @param d The deviation for calculation of sample size. 

#' @author Marco Aurelio Valles Leal
#'  
#' @examples
#' x=c(100000,50000,75000,200000,150000,175000,150000)
#' y=c(300000,200000,300000,600000,450000,520000,450000)
#' despesas.med=data.frame(area=c(1:7),x=x,y=y)
#' smp.est.razao(data=despesas.med,N=49)
#' 
#' 
#' @export


smp.size.razao = function(data=NULL,c.lev=95,N=NULL,d=NULL,mu=NULL){
  n                 =length(data[,1])
  sample.n          =n
  xpos              =which(tolower(names(data))=="x")
  ypos              =which(tolower(names(data))=="y")
  if(is.null(mu)){
    Xbarra            =mean(data[,xpos])}
  else{
    Xbarra            =mu}
  r                 =mean(data[,ypos])/mean(data[,xpos])
  yhat              =Xbarra*r
  if(is.null(N)){ythat="Tamanho da Populacao nao definido"}else{ythat=N*r*Xbarra}
  s2                =(1/(n-1))*sum((data[,ypos]-(r*data[,xpos]))**2)
  var.y             =(1/(n-1))*sum((data[,ypos]-(r*data[,xpos]))**2)*((N-n)/(n*N))
  var.r             =(1-(n/N))*((s2)/(n*mean(data[,xpos])**2))
  var.yt            =(N**2)*(Xbarra**2)*var.r
  if(n<30){
    statistic.val     =qt(p=.5+c.lev/200, df = sample.n-1 );statistic="t Student Statistic"
  if(is.null(d)){
    d <- statistic.val*sqrt((N-n)/N*s2/n)
    
  }
  n <- (N*statistic.val^2*s2)/(statistic.val^2*s2+N*d^2)
}
  else {
    statistic.val = qnorm(.5+c.lev/200);statistic="Score Statistic (Z)"
  if(is.null(d)){
  d <- statistic.val*sqrt(((N-n)/N)*s2/n)
  }
  n <- N*statistic.val^2*s2/(statistic.val)^2*s2+N*d^2
  
}
  
    
  
  METHOD = paste("Calculos para o Tamanho de Amostra do Estimador Razao")
  structure(list(
    "Population Size"                       = N,
    "Sample Size"                           = n,
    "Total X"                               = sum(data[,xpos]),
    "Total Y"                               = sum(data[,ypos]),
    "Estimated Value for (R)"               = r,
    "Var(R)"                                = var.r,
    "S2e"                                   = s2,
    "Statistic Used"                        = statistic,
    "Statistic Value"                       = statistic.val,
    "Error (d)"                             = d,
    "Tamanho da Amostra (n)"                = n,
    method = METHOD),
    class = "power.htest")
}