hor" href="#details"></a></h2>
    <p>By default, when the user tries to apply this function to nun-numeric variables, an error is raised. The exception is when the all variables are selected with the dot (like in <code>. ~ treat</code>. In this case, non-numeric variables are automatically omitted (with a message).</p>
<p>NAs are removed automatically: if the data contains NAs an information message will be prompted. First all observations containing NAs relating to the treatment or post variables are remo