diff --git a/css/stylesheet.css b/css/stylesheet.css
index 24cf570852e0faea7f3125519824a37ebd7f0f2b..3b8ed83b51227f048ccf856ca36b7658d6a63bd2 100644
--- a/css/stylesheet.css
+++ b/css/stylesheet.css
@@ -188,14 +188,14 @@ section {
 
 .data_container {
     top: 60px;
-    bottom: 70%;
+    bottom: 60%;
     left: 0;
     right: 0;
 }
 
 .code_container {
     left: 0;
-    top: 30%;
+    top: 40%;
     right: 0;
     bottom: 0;
 }
diff --git a/js/module/graph.js b/js/module/graph.js
index 7cf33af084d523f0fb1bcb808df0467328b8c22a..0f1a3807f754103abbcf773b9797fa479a79e17f 100644
--- a/js/module/graph.js
+++ b/js/module/graph.js
@@ -26,6 +26,7 @@ GraphTracer.prototype.clear = function () {
 GraphTracer.prototype.createRandomData = function (N, ratio) {
     Tracer.prototype.createRandomData.call(this, arguments);
 
+    if (!N) N = 5;
     if (!ratio) ratio = .3;
     var G = [];
     for (var i = 0; i < N; i++) {
@@ -39,9 +40,51 @@ GraphTracer.prototype.createRandomData = function (N, ratio) {
     return G;
 };
 
+GraphTracer.prototype.setTreeData = function (G, root) {
+    root = root || 0;
+    var maxDepth = -1;
+
+    var chk = [];
+    for (var i = 0; i < G.length; i++) chk.push(false);
+    var getDepth = function (node, depth) {
+        if (chk[node]) throw "the given graph is not a tree because it forms a circuit";
+        chk[node] = true;
+        if (maxDepth < depth) maxDepth = depth;
+        for (var i = 0; i < G[node].length; i++) {
+            if (G[node][i]) getDepth(i, depth + 1);
+        }
+    };
+    getDepth(root, 1);
+
+    if (this.setData(G, root)) return true;
+
+    var place = function (node, x, y) {
+        var temp = graph.nodes(n(node));
+        temp.x = x;
+        temp.y = y;
+    };
+
+    var wgap = 1 / (maxDepth - 1);
+    var dfs = function (node, depth, top, bottom) {
+        place(node, depth * wgap, (top + bottom) / 2);
+        var children = 0;
+        for (var i = 0; i < G[node].length; i++) {
+            if (G[node][i]) children++;
+        }
+        var vgap = (bottom - top) / children;
+        var cnt = 0;
+        for (var i = 0; i < G[node].length; i++) {
+            if (G[node][i]) dfs(i, depth + 1, top + vgap * cnt, top + vgap * ++cnt);
+        }
+    };
+    dfs(root, 0, 0, 1);
+
+    this.refresh();
+};
+
 // Override
 GraphTracer.prototype.setData = function (G) {
-    if (Tracer.prototype.setData.call(this, arguments)) return;
+    if (Tracer.prototype.setData.call(this, arguments)) return true;
 
     graph.clear();
     var nodes = [];
@@ -82,6 +125,8 @@ GraphTracer.prototype.setData = function (G) {
         ratio: 1
     });
     this.refresh();
+
+    return false;
 };
 
 GraphTracer.prototype._clear = function () {
diff --git a/js/module/weighted_graph.js b/js/module/weighted_graph.js
index 608be7439cc6b77b62fc5834c472a4e31f3ce9a5..5687ebc22e72a8aa87148375f9a6855762faab26 100644
--- a/js/module/weighted_graph.js
+++ b/js/module/weighted_graph.js
@@ -20,6 +20,7 @@ WeightedGraphTracer.prototype.clear = function () {
 WeightedGraphTracer.prototype.createRandomData = function (N, ratio, min, max) {
     Tracer.prototype.createRandomData.call(this, arguments);
 
+    if (!N) N = 5;
     if (!ratio) ratio = .3;
     if (!min) min = 1;
     if (!max) max = 5;
diff --git a/js/script.js b/js/script.js
index ee3313c42d7025efc08f575b6d7dea7ad86c6627..7cdcc73ae3aeeccd56a0a430ed5f01429ab66c00 100644
--- a/js/script.js
+++ b/js/script.js
@@ -20,8 +20,9 @@ dataEditor.on('change', function () {
 });
 
 var loadFile = function (category, algorithm, file, explanation) {
+    lastData = null;
     $('#explanation').html(explanation);
-    dataEditor.setValue('var G = [];', -1);
+    dataEditor.setValue('');
     codeEditor.setValue('');
 
     var dir = './algorithm/' + category + '/' + algorithm + '/' + file + '/';
@@ -49,7 +50,7 @@ var loadAlgorithm = function (category, algorithm) {
     $('#desc_ref').empty();
     $('.files_bar').empty();
     $('#explanation').html('');
-    dataEditor.setValue('var G = [];', -1);
+    dataEditor.setValue('');
     codeEditor.setValue('');
 
     var dir = './algorithm/' + category + '/' + algorithm + '/';
diff --git a/js/tracer.js b/js/tracer.js
index 88296cd949a7874f812c1034ec8ff777a376b3ba..f5bc1475a63fad0ad7cb21639ab397d58c05af7a 100644
--- a/js/tracer.js
+++ b/js/tracer.js
@@ -1,5 +1,5 @@
 var timer = null;
-var lastModule = null, lastData = null;
+var lastData = null;
 var stepLimit = 1e6;
 
 var Tracer = function (module) {
@@ -9,7 +9,6 @@ var Tracer = function (module) {
     this.traceOptions = null;
     this.traceIndex = -1;
     this.stepCnt = 0;
-    lastData = null;
 };
 
 Tracer.prototype.resize = function () {
@@ -31,8 +30,7 @@ Tracer.prototype.createRandomData = function (arguments) {
 
 Tracer.prototype.setData = function (arguments) {
     var data = JSON.stringify(arguments);
-    if (lastModule == this.module && lastData == data) return true;
-    lastModule = this.module;
+    if (lastData == data) return true;
     lastData = data;
     return false;
 };