title: When are factors necessary/appropriate in r
body: <p>I've been using the aov() function in R for ages. I always input my data via .csv files, and have never bothered converting any of the variables to 'factor'. </p>
  
  <p>Recently I've done just that, converting variables to factors and repeated the aov(), and the results of the aov() are now different. </p>
  
  <p>My data are ordered categories, 0,1,2. Un-ordered or ordered levels makes no difference, both are different than using the variable without converting to a factor. </p>
  
  <p>Are factors always appropriate? Why does this conversion make such a large difference? </p>
  
  <p>Please let me know if more information is necessary to make my question clearer. </p>