R/mtukey.test.R

Defines functions mtukey.test

Documented in mtukey.test

#' Modified Tukey Additivity Test
#' 
#' Test for an interaction in two-way ANOVA table by the modified Tukey test.
#'
#' @param Y data matrix
#' @param alpha level of the test
#' @param correction type of small sample size correction (0=none, 1=bootstrap without replacement, 2=sampling), see \code{Details}
#' @param Nboot number of simulations to be used for small sample size correction
#'
#' @return A list with class "\code{aTest}" containing the following components: 
#' test statistics \code{stat}, critical value \code{critical.value} and the result of 
#' the test \code{result}, i.e. whether the additivity hypothesis has been rejected.
#'
#' @details The level of the modified Tukey test is unstable for a small sample size. In such cases 
#' either bootstraping (\code{correction=1}) or sampling (\code{correction=2}) should be used to compute the critical value.
#' 
#' @references Simecek, Petr, and Simeckova, Marie. "Modification of Tukey's additivity test." 
#' \emph{Journal of Statistical Planning and Inference}, \bold{2012}.
#' 
#' @seealso \code{\link{tukey.test}}, \code{\link{mandel.test}}, \code{\link{johnson.graybill.test}}, 
#' \code{\link{lbi.test}}, \code{\link{johnson.graybill.test}}
#' 
#' @keywords htest
#'
#' @export
#' 
#' @examples
#' data(Boik)
#' mtukey.test(Boik)
#' mtukey.test(Boik,correction=2,Nboot=2000)

mtukey.test<-function(Y,alpha=0.05,correction=0,Nboot=1000)
{

  p.test<-function(data)
  {
    #dimension of data
    n.a<-nrow(data)
    n.b<-ncol(data)  
  
    #effects in submodel
    mu<-mean(data)
    r.effect<-apply(data,1,mean)-mu
    c.effect<-apply(data,2,mean)-mu
    
    #first estimate of k
    exp<-matrix(mu+rep(r.effect,n.b)+rep(c.effect,each=n.a),n.a,n.b)
    err<-data-exp
    k<-sum(cbind(r.effect)%*%rbind(c.effect)*err)/sum(cbind(r.effect)^2%*%rbind(c.effect)^2)
  
    #reestimation
    y<-data-mu-rep(c.effect,each=n.a)
    x<-matrix(1+k*rep(c.effect,each=n.a),n.a,n.b)
    a.new<-apply(x*y,1,sum)/apply(x^2,1,sum)
  
    y<-data-mu-rep(r.effect,n.b)
    x<-matrix(1+k*rep(r.effect,n.b),n.a,n.b)
    b.new<-apply(x*y,2,sum)/apply(x^2,2,sum)
  
    exp2<-matrix(mu+rep(a.new,n.b)+rep(b.new,each=n.a),n.a,n.b) 
    err2<-data-exp2
    k.new<-sum(cbind(a.new)%*%rbind(b.new)*err2)/sum(cbind(a.new)^2%*%rbind(b.new)^2)
  
    #compute statistics
    exp3<-matrix(mu+rep(a.new,n.b)+rep(b.new,each=n.a),n.a,n.b) + k.new*cbind(a.new)%*%rbind(b.new)
    err3<-data-exp3
  
    rss0<-sum(err^2)
    rss<-sum(err3^2)
    s<-rss/(n.a*n.b-n.a-n.b)
    loglik.ratio<-rss0/rss
    stat<-(loglik.ratio-1)*(n.a*n.b-n.a-n.b)/qf(1-alpha,1,n.a*n.b-n.a-n.b)
  
    return(c(stat,rss,s,loglik.ratio,abs(k.new)))
  }    

  #dimension of data
  n.a<-nrow(Y)
  n.b<-ncol(Y)  

  #effects in submodel
  mu<-mean(Y)
  r.effect<-apply(Y,1,mean)-mu
  c.effect<-apply(Y,2,mean)-mu
  
  #first estimate of k
  exp<-matrix(mu+rep(r.effect,n.b)+rep(c.effect,each=n.a),n.a,n.b)
  err<-Y-exp
  
  ppp<-p.test(Y)

  if (correction==0) out<-list(result=ppp[1]>1,stat=ppp[1],critical.value=1,alpha=alpha,name="Modified Tukey test")

  if (correction==1)
  {

     boot<-replicate(Nboot,p.test(exp+sample(err,n.a*n.b, replace=FALSE)))
     B<-apply(boot,1,quantile,probs=1-alpha)

     out<-list(result=ppp[1]>B[1],stat=ppp[1],critical.value=B[1],alpha=alpha,name="Modified Tukey test (small sample size correction, type 1)")
  }

  if (correction==2)
  {
    boot<-replicate(Nboot,p.test(exp+rnorm(n.a*n.b,sd=sqrt(ppp[3]))))
    B<-apply(boot,1,quantile,probs=1-alpha)
    out<-list(result=ppp[1]>B[1],stat=ppp[1],critical.value=B[1],alpha=alpha,name="Modified Tukey test (small sample size correction, type 2)")  
  }
 
  class(out)<-"aTest"
  return(out)
}

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additivityTests documentation built on May 29, 2017, 3:37 p.m.