R/oneway.R

In kimpham23/oneway: One-way Analysis of Variance

#' @title One Way Analysis of Variance
#' 
#' @description 
#' \code{oneway} computes a one-way analysis of variance
#' and inclues group level summary statistics.
#' 
#' @details
#' This function computes a standard one-way ANOVA, means,
#' and standard deviations. Missing values are handled via
#' listwise deletion.
#' 
#' @param formula an object of class formula, relating the dependent
#' variable to the grouping variable
#' @param data a data frame contain the variables in the model.
#' 
#' @export
#' 
#' @return a list with 2 elements:
#' \item{oneway}{a list with the lm results}
#' \item{summarystats}{a data frame with the summary statistics}
#' 
#' @author Rob Kabacoff <rkabacoff@@wesleyan.edu>
#' 
#' @examples
#' mileage <- oneway(hwy ~ class, cars)
#' summary(mileage)
#' mileage
#' plot(mileage)

oneway <- function(formula, data) {
  
  # listwise deletion of missing values
  data_complete <- na.omit(data)
  
  # anova
  fit <- lm(formula, data_complete)
  
  stats <-  aggregate(formula,
                     data,
                     function(x) c(n = length(x), mean = mean(x), sd = sd(x)))
 
  
  result <- list(anova = fit, summarystats = stats)
  class(result) <- c("oneway", "list")
  return(result)
  
}