R/produce_2_by_k_counts_table.R

In msxakk89/dat: Data Analyst Toolkit (dat): a library of tools for data analysts and scientists

#' Create 2 by k count table  
#' 
#' This function takes in a data frame where the first column is a vector of 2 categories, while the second column is a vector of redundant k cases. 
#' 
#' @param df A data frame where df[,1] is a vector of two categories (e.g. "A","B"), while df[,2] is a vector of redundant cases (e.g. "Q","Q").
#' @return A 2xk table of counts in the 2 categories.
#' @export 
produce_2_by_k_counts_table <- function(df){
  df <- changeTypeOfColumns(df,1:2,"character")
  two_categories <- unique(df[,1])
  if(!(length(two_categories)==2)){
    stop("There are more than two categories in df[,1]. Exiting.")
  }
  k_categories <- unique(df[,2])
  out <- matrix(nrow = 2, ncol = length(k_categories))
  for(i in 1:length(k_categories)){
    category_1 <- nrow(df[df[,1]==two_categories[1] & df[,2]==k_categories[i],]) # count of category 1 & k category i
    category_2 <- nrow(df[df[,1]==two_categories[2] & df[,2]==k_categories[i],]) # count of category 2 & k category i
    out[1,i] <- category_1
    out[2,i] <- category_2
  }
  row.names(out) <- two_categories
  colnames(out) <- k_categories
  return(out)
}