R/anova2x2.R

In pwr2ppl: Power Analyses for Common Designs (Power to the People)

#'Compute power for a Two by Two Between Subjects ANOVA.
#'Takes means, sds, and sample sizes for each group. Alpha is .05 by default, alternative values may be entered by user
#'@param m1.1 Cell mean for First level of Factor A, First level of Factor B
#'@param m1.2 Cell mean for First level of Factor A, Second level of Factor B
#'@param m2.1 Cell mean for Second level of Factor A, First level of Factor B
#'@param m2.2 Cell mean for Second level of Factor A, Second level of Factor B
#'@param s1.1 Cell standard deviation for First level of Factor A, First level of Factor B
#'@param s1.2 Cell standard deviation for First level of Factor A, Second level of Factor B
#'@param s2.1 Cell standard deviation for Second level of Factor A, First level of Factor B
#'@param s2.2 Cell standard deviation for Second level of Factor A, Second level of Factor B
#'@param n1.1 Cell sample size for First level of Factor A, First level of Factor B
#'@param n1.2 Cell sample size for First level of Factor A, Second level of Factor B
#'@param n2.1 Cell sample size for Second level of Factor A, First level of Factor B
#'@param n2.2 Cell sample size for Second level of Factor A, Second level of Factor B
#'@param alpha Type I error (default is .05)
#'@param all Power(ALL) - Power for detecting all predictors in the model at once (default is "OFF")
#'@examples
#'anova2x2(m1.1=0.85, m1.2=0.85, m2.1=0.00, m2.2=0.60,
#'s1.1=1.7, s1.2=1.7, s2.1=1.7, s2.2=1.7,
#'n1.1=100, n1.2=100, n2.1=100, n2.2=100, alpha=.05)
#'anova2x2(m1.1=0.85, m1.2=0.85, m2.1=0.00, m2.2=0.60,
#'s1.1=1.7, s1.2=1.7, s2.1=1.7, s2.2=1.7,
#'n1.1=100, n1.2=100, n2.1=100, n2.2=100,
#'alpha=.05, all="ON")
#'@return Power for the Two Factor ANOVA
#'@export

anova2x2<-function(m1.1=NULL,m1.2=NULL,m2.1=NULL,m2.2=NULL, s1.1=NULL,s1.2=NULL,s2.1=NULL,s2.2=NULL,
                         n1.1=NULL,n1.2=NULL,n2.1=NULL,n2.2=NULL, alpha=.05, all="OFF"){

  oldoption<-options(contrasts=c("contr.helmert", "contr.poly"))
  oldoption
  on.exit(options(oldoption))
  x<-stats::rnorm(n1.1,m1.1,s1.1)
  X<-x
  MEAN<-m1.1
  SD<-s1.1
  Z <- (((X - mean(X, na.rm = TRUE))/stats::sd(X, na.rm = TRUE))) * SD
  y<-MEAN + Z
  A<-rep("A1",n1.1)
  B<-rep("B1",n1.1)
  l1.1<-data.frame(y, A, B)
  x<-stats::rnorm(n1.2,m1.2,s1.2)
  X<-x
  MEAN<-m1.2
  SD<-s1.2
  Z <- (((X - mean(X, na.rm = TRUE))/stats::sd(X, na.rm = TRUE))) * SD
  y<-MEAN + Z
  A<-rep("A1",n1.2)
  B<-rep("B2",n1.2)
  l1.2<-data.frame(y, A, B)
  x<-stats::rnorm(n2.1,m2.1,s2.1)
  X<-x
  MEAN<-m2.1
  SD<-s2.1
  Z <- (((X - mean(X, na.rm = TRUE))/stats::sd(X, na.rm = TRUE))) * SD
  y<-MEAN + Z
  A<-rep("A2",n2.1)
  B<-rep("B1",n2.1)
  l2.1<-data.frame(y, A, B)
  x<-stats::rnorm(n2.2,m2.2,s2.2)
  X<-x
  MEAN<-m2.2
  SD<-s2.2
  Z <- (((X - mean(X, na.rm = TRUE))/stats::sd(X, na.rm = TRUE))) * SD
  y<-MEAN + Z
  A<-rep("A2",n2.2)
  B<-rep("B2",n2.2)
  l2.2<-data.frame(y, A, B)
  simdat<-rbind(l1.1,l1.2,l2.1,l2.2)
  anova<-stats::aov(y~A*B, data=simdat)
  anova<-car::Anova(anova, type="III")
  SSA<-anova[2,1] #column, row
  SSB<-anova[3,1]
  SSAB<-anova[4,1]
  SSwin<-anova[5,1]
  dfA<-anova[2,2]
  dfB<-anova[3,2]
  dfAB<-anova[4,2]
  dfwin<-anova[5,2]
  MSwin<-SSwin/dfwin
  eta2A<-SSA/(SSA+SSwin)
  f2A<-eta2A/(1-eta2A)
  lambdaA<-f2A*dfwin
  minusalpha<-1-alpha
  FtA<-stats::qf(minusalpha, dfA, dfwin)
  power.A<-round(1-stats::pf(FtA, dfA,dfwin,lambdaA),3)
  eta2B<-SSB/(SSB+SSwin)
  f2B<-eta2B/(1-eta2B)
  lambdaB<-f2B*dfwin
  FtB<-stats::qf(minusalpha, dfB, dfwin)
  power.B<-round(1-stats::pf(FtB, dfB,dfwin,lambdaB),3)
  eta2AB<-SSAB/(SSAB+SSwin)
  f2AB<-eta2AB/(1-eta2AB)
  lambdaAB<-f2AB*dfwin
  FtAB<-stats::qf(minusalpha,dfAB, dfwin)
  power.AB<-round(1-stats::pf(FtAB,dfAB,dfwin,lambdaAB),3)
  power.All<-round((power.A*power.B*power.AB),3)
  nall<-n1.1+n1.2+n2.1+n2.2
  eta2A<-round((eta2A),4)
  eta2B<-round((eta2B),4)
  eta2AB<-round((eta2AB),4)


  if (all=="OFF")
  {message("Power for Main Effect Factor A = ", power.A)
   message("Power for Main Effect Factor B = ", power.B)
   message("Power for Interaction AxB = ", power.AB)
   result <- data.frame(matrix(ncol = 7))
   colnames(result) <- c( "nall","Eta-squared A","Power A", "Eta-squared B", "Power B","Eta-squared AxB", "Power AxB")
   result[, 1]<-nall
   result[, 2]<-eta2A
   result[, 3]<-power.A
   result[, 4]<-eta2B
   result[, 5]<-power.B
   result[, 6]<-eta2AB
   result[, 7]<-power.AB
   output<-na.omit(result)
   rownames(output)<- c()
}
  if (all=="ON")
  {message("Power for Main Effect Factor A = ", power.A)
    message("Power for Main Effect Factor B = ", power.B)
    message("Power for Interaction AxB = ", power.AB)
    message("Power(All)=", power.All)
    result <- data.frame(matrix(ncol = 8))
    colnames(result) <- c( "nall","Eta-squared A","Power A", "Eta-squared B", "Power B","Eta-squared AxB", "Power AxB","Power All")
    result[, 1]<-nall
    result[, 2]<-eta2A
    result[, 3]<-power.A
    result[, 4]<-eta2B
    result[, 5]<-power.B
    result[, 6]<-eta2AB
    result[, 7]<-power.AB
    result[, 8]<-power.All
    output<-na.omit(result)
    rownames(output)<- c()
  }
invisible(output)
  }