Options for Creating Dummy Variables

dummy_variables.R

library(magrittr)
    
    dummy_ifelse <- function(x)
    {
      if (!is.factor(x)) stop("x is not a factor")
      
      lev <- levels(x)
      
      lapply(lev[-1],
             function(l) ifelse(x %in% l, 1, 0)) %>%
        setNames(lev[-1]) %>%
        as.data.frame()
    }
    
    
    dummy_arith <- function(x)
    {
      if (!is.factor(x)) stop("x is not a factor")
      
      lev <- levels(x)
      
      lapply(lev[-1],
             function(l) x %in% l + 0L) %>%
        setNames(lev[-1]) %>%
        as.data.frame()
    }
    
    dummy_list <- function(x)
    {
      if (!is.factor(x)) stop("x is not a factor")
      
      lev <- levels(x)
      
      lapply(lev[-1],
             function(l)
             {
               y <- x
               levels(y) <- list("1" = l,
                                 "0" = levels(y)[!levels(y) %in% l])
               as.numeric(as.character(y))
             }) %>%
        setNames(lev[-1]) %>%
        as.data.frame()
    }
    
    library(microbenchmark)
    microbenchmark(
      ifelse = dummy_ifelse(iris$Species),
      arith = dummy_arith(iris$Species),
      list_m = dummy_list(iris$Species),
      model_mat = model.matrix(~iris$Species) %>% as.data.frame
    )