logisticRegressionR2s.R

#function to compute R2s in logistic regression
logisticR2s <- function(logisticModel) {
    modelDeviance <- logisticModel$deviance 
    nullDeviance <- logisticModel$null.deviance
    n <- length(logisticModel$fitted.values)
    
    R2HosmerLemeshow <- 1 - modelDeviance / nullDeviance
    R2CoxSnell <- 1 - exp((modelDeviance - nullDeviance) / n) 
    R2Nagelkerke <- R2CoxSnell / (1 - exp( - (nullDeviance / n)))
    
    col1 <- c("Hosmer and Lemeshow", "Cox and Snell", "Nagelkerke")
    col2 <- c(R2HosmerLemeshow, R2CoxSnell, R2Nagelkerke)
    col3 <- col2 * 100
    
    return(data.frame(RSquaredType = col1,
               Value = round(col2, 2),
               Percent = round(col3, 2)))
}