R/betaABfromMeanSD.R

In ThomasWilli/politantheme: Provides a theme for the politan.ch blog

##' Politan Color Theme
##' @export
##' 




betaABfromMeanSD = function( mean , sd ) {
  if ( mean <=0 | mean >= 1) stop("must have 0 < mean < 1")
  if ( sd <= 0 ) stop("sd must be > 0")
  kappa = mean*(1-mean)/sd^2 - 1
  if ( kappa <= 0 ) stop("invalid combination of mean and sd")
  a = mean * kappa
  b = ( 1.0 - mean ) * kappa
  return( list( a=a , b=b ) )
}