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我正在尝试从 heartology-weka.arff 了解 WEKA J48 决策树。

我已经运行了如下输出，

Test mode:10-fold cross-validation

=== Classifier model (full training set) ===

J48 pruned tree
------------------

thal = Rev
|   chest-pain-type = Asymptomatic: Sick (79.0/7.0)
|   chest-pain-type = AbnormalAngina
|   |   #colored-vessels = 0
|   |   |   peak <= 0.1: Healthy (4.0)
|   |   |   peak > 0.1: Sick (3.0/1.0)
|   |   #colored-vessels = 1: Sick (2.0)
|   |   #colored-vessels = 2: Healthy (0.0)
|   |   #colored-vessels = 3: Healthy (0.0)
|   chest-pain-type = Angina
|   |   cholesterol <= 229: Healthy (3.0)
|   |   cholesterol > 229
|   |   |   age <= 48: Sick (2.0)
|   |   |   age > 48: Healthy (3.0/1.0)
|   chest-pain-type = NoTang
|   |   slope = Flat
|   |   |   #colored-vessels = 0
|   |   |   |   blood-pressure <= 122: Healthy (3.0)
|   |   |   |   blood-pressure > 122: Sick (3.0)
|   |   |   #colored-vessels = 1: Sick (5.0)
|   |   |   #colored-vessels = 2: Sick (0.0)
|   |   |   #colored-vessels = 3: Sick (3.0/1.0)
|   |   slope = Up: Healthy (7.0/1.0)
|   |   slope = Down: Healthy (1.0)
thal = Normal
|   #colored-vessels = 0: Healthy (118.0/12.0)
|   #colored-vessels = 1
|   |   sex = Male
|   |   |   chest-pain-type = Asymptomatic: Sick (9.0)
|   |   |   chest-pain-type = AbnormalAngina: Sick (2.0/1.0)
|   |   |   chest-pain-type = Angina: Healthy (3.0/1.0)
|   |   |   chest-pain-type = NoTang: Healthy (2.0)
|   |   sex = Female: Healthy (13.0/1.0)
|   #colored-vessels = 2
|   |   angina = TRUE: Sick (3.0)
|   |   angina = FALSE
|   |   |   age <= 62
|   |   |   |   age <= 53: Healthy (2.0)
|   |   |   |   age > 53: Sick (4.0)
|   |   |   age > 62: Healthy (5.0)
|   #colored-vessels = 3: Sick (6.0/1.0)
thal = Fix
|   #colored-vessels = 0
|   |   angina = TRUE: Sick (3.0/1.0)
|   |   angina = FALSE: Healthy (5.0)
|   #colored-vessels = 1: Sick (4.0)
|   #colored-vessels = 2: Sick (4.0)
|   #colored-vessels = 3: Sick (2.0)

Number of Leaves  :     32

Size of the tree :  49


Time taken to build model: 0.03 seconds

=== Stratified cross-validation ===
=== Summary ===

Correctly Classified Instances         222               73.2673 %
Incorrectly Classified Instances        81               26.7327 %
Kappa statistic                          0.4601
Mean absolute error                      0.3067
Root mean squared error                  0.4661
Relative absolute error                 61.8185 %
Root relative squared error             93.5807 %
Total Number of Instances              303     

=== Detailed Accuracy By Class ===

               TP Rate   FP Rate   Precision   Recall  F-Measure   ROC Area  Class
                 0.696     0.236      0.711     0.696     0.703      0.756    Sick
                 0.764     0.304      0.75      0.764     0.757      0.756    Healthy
Weighted Avg.    0.733     0.273      0.732     0.733     0.732      0.756

=== Confusion Matrix ===

   a   b   <-- classified as
  96  42 |   a = Sick
  39 126 |   b = Healthy

问题是

  • j48选择什么属性作为顶层决策树节点？
  • 绘制一个图表，显示 J48 创建的决策树的前两个级别的属性和值。

到目前为止，我只能解释关于正确分类类的混淆矩阵。任何帮助，将不胜感激。

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1 回答 1

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最顶层的节点是“thal”，它具有三个不同的级别。

您可以使用“可视化树”在 weka 中将树绘制为图表。在模型结果上，左键单击或右键单击显示“J48 - 20151206 10:33”（或类似内容）的项目。亲自尝试或搜索我提供屏幕截图的答案（关于如何执行此操作）

您可以通过在 J48 配置对话框中将树“修剪”到 n 级来限制树。

于 2015-12-13T21:01:48.217 回答