diff --git a/docs/03-data-management.html b/docs/03-data-management.html
index ac0d41a..f72ec11 100644
--- a/docs/03-data-management.html
+++ b/docs/03-data-management.html
@@ -17,7 +17,7 @@
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-  margin: 0 0.8em 0.2em -1em; /* quarto-specific, see https://github.com/quarto-dev/quarto-cli/issues/4556 */ 
+  margin: 0 0.8em 0.2em -1em; /* quarto-specific, see https://github.com/quarto-dev/quarto-cli/issues/4556 */
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 /* CSS for syntax highlighting */
@@ -105,7 +105,6 @@
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-        <a class="flex-grow-1" role="button" data-bs-toggle="collapse" data-bs-target=".quarto-sidebar-collapse-item" aria-controls="quarto-sidebar" aria-expanded="false" aria-label="Toggle sidebar navigation" onclick="if (window.quartoToggleHeadroom) { window.quartoToggleHeadroom(); }">      
+        <a class="flex-grow-1" role="button" data-bs-toggle="collapse" data-bs-target=".quarto-sidebar-collapse-item" aria-controls="quarto-sidebar" aria-expanded="false" aria-label="Toggle sidebar navigation" onclick="if (window.quartoToggleHeadroom) { window.quartoToggleHeadroom(); }">
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     <div class="pt-lg-2 mt-2 text-left sidebar-header">
     <div class="sidebar-title mb-0 py-0">
-      <a href="./">Introduction to Stata</a> 
+      <a href="./">Introduction to Stata</a>
         <div class="sidebar-tools-main">
   <a href="" class="quarto-color-scheme-toggle quarto-navigation-tool  px-1" onclick="window.quartoToggleColorScheme(); return false;" title="Toggle dark mode"><i class="bi"></i></a>
 </div>
@@ -172,46 +171,46 @@
         <div id="quarto-search" class="" title="Search"></div>
         </div>
         </div>
-    <div class="sidebar-menu-container"> 
+    <div class="sidebar-menu-container">
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-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
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  <span class="menu-text">Preface</span></a>
   </div>
 </li>
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-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
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   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
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   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
   <a href="./03-data-management.html" class="sidebar-item-text sidebar-link active">
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   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
   <a href="./04-data-manipulation.html" class="sidebar-item-text sidebar-link">
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   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
   <a href="./05-programming.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text"><span class="chapter-number">5</span>&nbsp; <span class="chapter-title">Programming &amp; Advanced Features</span></span></a>
   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
   <a href="./appendix.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text">Appendix</span></a>
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@@ -224,7 +223,7 @@
     <div id="quarto-margin-sidebar" class="sidebar margin-sidebar">
         <nav id="TOC" role="doc-toc" class="toc-active">
     <h2 id="toc-title">Table of contents</h2>
-   
+
   <ul>
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@@ -258,11 +257,11 @@ <h1 class="title"><span class="chapter-number">3</span>&nbsp; <span class="chapt
 
 <div class="quarto-title-meta">
 
-    
-  
-    
+
+
+
   </div>
-  
+
 
 
 </header>
@@ -855,7 +854,7 @@ <h2 data-number="3.9" class="anchored" data-anchor-id="exercise-4"><span class="
       toggleBodyColorMode(bsSheetEl);
     }
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-  toggleBodyColorPrimary();  
+  toggleBodyColorPrimary();
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@@ -928,7 +927,7 @@ <h2 data-number="3.9" class="anchored" data-anchor-id="exercise-4"><span class="
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+          toggle.classList.add("alternate");
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@@ -942,13 +941,13 @@ <h2 data-number="3.9" class="anchored" data-anchor-id="exercise-4"><span class="
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+      }, 40);
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-  const hasAlternateSentinel = () => {  
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   window.quartoToggleColorScheme = () => {
-    // Read the current dark / light value 
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@@ -1009,7 +1008,7 @@ <h2 data-number="3.9" class="anchored" data-anchor-id="exercise-4"><span class="
   anchorJS.add('.anchored');
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       button.setAttribute("data-bs-placement", "left");
       button.setAttribute("data-bs-title", "Copied!");
-      tooltip = new bootstrap.Tooltip(button, 
-        { trigger: "manual", 
+      tooltip = new bootstrap.Tooltip(button,
+        { trigger: "manual",
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           offset: [0, -8]});
-      tooltip.show();    
+      tooltip.show();
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@@ -1082,7 +1081,7 @@ <h2 data-number="3.9" class="anchored" data-anchor-id="exercise-4"><span class="
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     }
-    window.tippy(el, config); 
+    window.tippy(el, config);
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@@ -1154,7 +1153,7 @@ <h2 data-number="3.9" class="anchored" data-anchor-id="exercise-4"><span class="
     tippyHover(xref, undefined, function(instance) {
       instance.disable();
       let url = xref.getAttribute('href');
-      let hash = undefined; 
+      let hash = undefined;
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@@ -1182,7 +1181,7 @@ <h2 data-number="3.9" class="anchored" data-anchor-id="exercise-4"><span class="
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-            } 
+            }
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-          } 
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             height = bottom - top;
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-            // cook up a div (if necessary) and position it 
+            // cook up a div (if necessary) and position it
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               div = window.document.createElement("div");
@@ -1371,7 +1370,7 @@ <h2 data-number="3.9" class="anchored" data-anchor-id="exercise-4"><span class="
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         <i class="bi bi-arrow-left-short"></i> <span class="nav-page-text"><span class="chapter-number">2</span>&nbsp; <span class="chapter-title">Working with Data Sets</span></span>
-      </a>          
+      </a>
   </div>
   <div class="nav-page nav-page-next">
       <a href="./04-data-manipulation.html" class="pagination-link" aria-label="<span class='chapter-number'>4</span>&nbsp; <span class='chapter-title'>Data Manipulation</span>">
@@ -1384,4 +1383,4 @@ <h2 data-number="3.9" class="anchored" data-anchor-id="exercise-4"><span class="
 
 
 
-</body></html>
\ No newline at end of file
+</body></html>
diff --git a/docs/04-data-manipulation.html b/docs/04-data-manipulation.html
index c2157b5..9cc3335 100644
--- a/docs/04-data-manipulation.html
+++ b/docs/04-data-manipulation.html
@@ -17,7 +17,7 @@
 ul.task-list{list-style: none;}
 ul.task-list li input[type="checkbox"] {
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-  margin: 0 0.8em 0.2em -1em; /* quarto-specific, see https://github.com/quarto-dev/quarto-cli/issues/4556 */ 
+  margin: 0 0.8em 0.2em -1em; /* quarto-specific, see https://github.com/quarto-dev/quarto-cli/issues/4556 */
   vertical-align: middle;
 }
 /* CSS for syntax highlighting */
@@ -105,7 +105,6 @@
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 }</script>
 
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   <script src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml-full.js" type="text/javascript"></script>
 
 <script type="text/javascript">
@@ -147,7 +146,7 @@
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+        <a class="flex-grow-1" role="button" data-bs-toggle="collapse" data-bs-target=".quarto-sidebar-collapse-item" aria-controls="quarto-sidebar" aria-expanded="false" aria-label="Toggle sidebar navigation" onclick="if (window.quartoToggleHeadroom) { window.quartoToggleHeadroom(); }">
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         <i class="bi bi-search"></i>
@@ -161,7 +160,7 @@
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     <div class="pt-lg-2 mt-2 text-left sidebar-header">
     <div class="sidebar-title mb-0 py-0">
-      <a href="./">Introduction to Stata</a> 
+      <a href="./">Introduction to Stata</a>
         <div class="sidebar-tools-main">
   <a href="" class="quarto-color-scheme-toggle quarto-navigation-tool  px-1" onclick="window.quartoToggleColorScheme(); return false;" title="Toggle dark mode"><i class="bi"></i></a>
 </div>
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         <div id="quarto-search" class="" title="Search"></div>
         </div>
         </div>
-    <div class="sidebar-menu-container"> 
+    <div class="sidebar-menu-container">
     <ul class="list-unstyled mt-1">
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
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  <span class="menu-text">Preface</span></a>
   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
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   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
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  <span class="menu-text"><span class="chapter-number">2</span>&nbsp; <span class="chapter-title">Working with Data Sets</span></span></a>
   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
   <a href="./03-data-management.html" class="sidebar-item-text sidebar-link">
  <span class="menu-text"><span class="chapter-number">3</span>&nbsp; <span class="chapter-title">Data Management</span></span></a>
   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
   <a href="./04-data-manipulation.html" class="sidebar-item-text sidebar-link active">
  <span class="menu-text"><span class="chapter-number">4</span>&nbsp; <span class="chapter-title">Data Manipulation</span></span></a>
   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
   <a href="./05-programming.html" class="sidebar-item-text sidebar-link">
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   </div>
 </li>
         <li class="sidebar-item">
-  <div class="sidebar-item-container"> 
+  <div class="sidebar-item-container">
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  <span class="menu-text">Appendix</span></a>
   </div>
@@ -224,7 +223,7 @@
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         <nav id="TOC" role="doc-toc" class="toc-active">
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+
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@@ -273,11 +272,11 @@ <h1 class="title"><span class="chapter-number">4</span>&nbsp; <span class="chapt
 
 <div class="quarto-title-meta">
 
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-  
-    
+
+
+
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+      }, 40);
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+    // Read the current dark / light value
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@@ -1819,7 +1818,7 @@ <h2 data-number="4.11" class="anchored" data-anchor-id="reshaping-files"><span c
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       button.setAttribute("data-bs-placement", "left");
       button.setAttribute("data-bs-title", "Copied!");
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+    window.tippy(el, config);
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   const noterefs = window.document.querySelectorAll('a[role="doc-noteref"]');
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-            // cook up a div (if necessary) and position it 
+            // cook up a div (if necessary) and position it
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@@ -2181,7 +2180,7 @@ <h2 data-number="4.11" class="anchored" data-anchor-id="reshaping-files"><span c
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   </div>
   <div class="nav-page nav-page-next">
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@@ -2194,4 +2193,4 @@ <h2 data-number="4.11" class="anchored" data-anchor-id="reshaping-files"><span c
 
 
 
-</body></html>
\ No newline at end of file
+</body></html>