private static void ParseDataLine(string line, ref Instances data)
{
List<string> valueList = ParseValueList(line);
if (null == valueList
|| 0 == valueList.Count)
{
throw new Exception("Unexpected exception");
}
data.AddInstance(valueList);
if (data.Examples.Length % 1000 == 0)
{
// output some progress
Logger.Log(LogLevel.Progress, " {0}", data.Examples.Length);
}
}
/// <summary>
/// Reads and parses the data stream in arff format into an instance of class Instances.
/// </summary>
/// <param name="dataStream">data stream with arff data</param>
/// <param name="classAttributeName">name of the attribute to be used as class</param>
/// <returns>object containing all training data</returns>
public static Instances Read(StreamReader dataStream, string classAttributeName)
{
if (null == dataStream)
{
throw new ArgumentNullException("dataStream");
}
Instances data = new Instances();
data.AddClassAttribute(classAttributeName);
// move to the start of the stream - just in case
dataStream.BaseStream.Seek(0, SeekOrigin.Begin);
bool readingData = false;
while (!dataStream.EndOfStream)
{
string line = dataStream.ReadLine();
if (string.IsNullOrWhiteSpace(line))
{
// skip over empty lines
continue;
}
// is this the data header
if (line.Equals(DataSectionMarker))
{
readingData = true;
continue;
}
// process the line
if (!readingData)
{
ParseMetadataLine(line, ref data);
}
else
{
ParseDataLine(line, ref data);
}
}
return data;
}
/// <summary>
/// Learns a decision tree model for the data passed as arguments
/// </summary>
/// <param name="data">training data</param>
/// <returns>decision tree</returns>
public Node Learn(Instances data)
{
if (null == data
|| null == data.Examples
|| null == data.Attributes
|| null == data.ClassAttribute)
{
throw new ArgumentException("data");
}
Logger.Log(LogLevel.Progress, "Running ID3Lerner ");
// adjust the attribute list
var attributeList = data.Attributes.Where(a => !a.Name.Equals(data.ClassAttribute.Name));
if (this.handleUnknownAsValue)
{
attributeList = attributeList.Select(a =>
{
List<string> values = a.Values.ToList();
values.Add(Instances.UnknownValue);
return new Arff.Attribute()
{
Name = a.Name,
Values = values.ToArray()
};
});
}
Node dt = Learn(
data.Examples,
attributeList.ToArray(),
data.ClassAttribute);
Logger.Log(LogLevel.Progress, " Done{0}", System.Console.Out.NewLine);
return dt;
}
/// <summary>
/// Computes the accuracy of the classifier on the data set passed as a parameter.
/// </summary>
/// <param name="data">test data to evaluate classifier on</param>
/// <returns>number between 0.0 and 1.0 representing the accuracy</returns>
public double Evaluate(Instances data)
{
if (null == data
|| null == data.ClassAttribute)
{
throw new ArgumentNullException("data");
}
Logger.Log(LogLevel.Progress, "Running Accuracy Evaluator ");
int correct = 0;
foreach (Instance example in data.Examples)
{
string predictedClass = this.classifier.Classify(example);
string actualClass = example.Data[data.ClassAttribute.Name];
if (predictedClass == actualClass)
{
correct++;
}
}
Logger.Log(LogLevel.Progress, " Done{0}", System.Console.Out.NewLine);
return (double)correct / (double)data.Examples.Length;
}
private void TrainAndEvaluateClassifier(Instances data, Instances testData, double splitStoppingConfidence, bool useGainRatio)
{
// learn the tree
ID3Learner learner = new ID3Learner(splitStoppingConfidence, true, useGainRatio);
Node decisionTree = learner.Learn(data);
// output the tree
File.WriteAllText(
string.Format("{0}_DTID3_{1}_{2}.txt", Path.GetFileNameWithoutExtension(this.trainingDataFilePath), useGainRatio, splitStoppingConfidence.ToString("0.0000")),
decisionTree.ToString());
// evaluate the classifier
DTClassifier classifier = new DTClassifier(decisionTree);
AccuracyEvaluator evaluator = new AccuracyEvaluator(classifier);
double accuracy = evaluator.Evaluate(testData);
this.reportData.Add(
string.Format("{0}\t\t\t{1}\t\t{2}{3}", splitStoppingConfidence.ToString("0.0000"), useGainRatio, accuracy.ToString("0.0000"), System.Console.Out.NewLine));
}
private static void ParseMetadataLine(string line, ref Instances data)
{
// the only metadata lines we care about are attributes
Match attributeMatch = AttributeLineRegex.Match(line);
if (!attributeMatch.Success)
{
return;
}
// retrieve the data
string attributeName = attributeMatch.Groups["Name"].Value;
string attributeValueList = attributeMatch.Groups["Values"].Value;
// lets parse the value list
List<string> valueList = ParseValueList(attributeValueList);
if (null == valueList
|| 0 == valueList.Count)
{
throw new Exception("Unexpected exception");
}
// add the attribute definition
data.AddAttribute(attributeName, valueList);
}
