/span><span class="op">(</span></span>
<span>  Y <span class="op">=</span> <span class="cn">NULL</span>,</span>
<span>  X <span class="op">=</span> <span class="cn">NULL</span>,</span>
<span>  f1 <span class="op">=</span> <span class="cn">NULL</span>,</span>
<span>  f2 <span class="op">=</span> <span class="cn">NULL</span>,</span>
<span>  indx <span class="op">=</span> <span class="fl">1</span>,</span>
<span>  type <span class="op">=</span> <span class="st">"r_squared"</span>,</span>
<span>  run_regression 