Addition to docs

Author: hosseinmoein

docs/HTML/DataFrame.html

@@ -1629,6 +1629,10 @@ <H2 ID="2"><font color="blue">API Reference with code samples <font size="+4">&#
       <td title="Memory usage structure">struct <a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/get_memory_usage.html">MemUsage</a>{}</td>
     </tr>
 
+    <tr class="item" onmouseover="this.style.backgroundColor='#ffff66';" onmouseout="this.style.backgroundColor='#d4e3e5';">
+      <td title="structure containing the parameteres to pca_by_eigen() call">struct <a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/pca_by_eigen.html">PCAParams</a>{}</td>
+    </tr>
+
     <tr class="item" onmouseover="this.style.backgroundColor='#ffff66';" onmouseout="this.style.backgroundColor='#d4e3e5';">
       <td title="Parameters to make_stationary() function">struct <a href="https://htmlpreview.github.io/?https://github.com/hosseinmoein/DataFrame/blob/master/docs/HTML/make_stationary.html">StationaryParams</a>{}</td>
     </tr>