title: what does "~0" mean in the R model matrix
body: <p>I am trying to understand model matrix in R (model.matrix), to convert categorical variables to dummy variables and came across the following code</p>
  
  <pre><code># Option 2: use model.matrix() to convert all categorical variables in the data frame into a set of dummy variables. We must then turn the resulting data matrix back into 
  # a data frame for further work.
  xtotal &lt;- model.matrix(~ 0 + REMODEL, data = df)
  xtotal &lt;- as.data.frame(xtotal)
  </code></pre>
  
  <p>Can someone please help me understand what "~0" here mean ? And what the code is trying to do ? </p>