R/invlogit.R

In helophilus/ColsTools: A variety of convenience tools and short-cuts

#' inverse logit function using glm model parameters
#'
#' \code{invlogit(modint=NULL,slope=NULL,xval=NULL)}
#'
#' @param modint is binomial glm model intercept
#' @param slope is binomial glm model slope
#' @param xval is the value for which you want the inverse logit

invlogit=function(modint=NULL,slope=NULL,xval=NULL){
  if(class(modint)[1]=='numeric'){
    a=modint;b=slope
  } else {
    a=modint$coef[1];b=modint$coef[2]
    xval=slope
  }
  I=exp(a+b*xval)/(1+(exp(a+b*xval)))
  return(as.numeric(I))
}