TimeSeries Forecasting Weka - Java API

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I am trying to implement TimeSeries Forecasting in a JavaService in webMethods. My Code is not working and i am completely lost so i would be glad if you could help me! FYI: I used this Tutorial.

This is the Exception i get: com.wm.lang.flow.FlowException: weka.core.expressionlanguage.parser.Parser.getSymbolFactory()Ljava_cup/runtime/SymbolFactory;

I just post the part which is not webMethods specific (normal Java):

In the first part i am building an ARFF File which works fine. Because i saved the file and opened it with the weka Explorer and everything looks fine.

The ARFF file looks like this:

@relation Rel
@attribute Count numeric
@data
2758
2797
2861
575
505
4029

(just with some more values (59 in total)) I want to forecast the next 3 values.

Forecasting Part:


// At the berginning i create and save the arff file, so i have an Instances 
object called 'dataset'

WekaForecaster forecaster = new WekaForecaster();
try {
     forecaster.setFieldsToForecast("Count");
} catch (Exception e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}

forecaster.setBaseForecaster(new GaussianProcesses());
forecaster.getTSLagMaker().setTimeStampField("Date");
forecaster.getTSLagMaker().setMinLag(1);
forecaster.getTSLagMaker().setMaxLag(12);
forecaster.getTSLagMaker().setAddMonthOfYear(true);
forecaster.getTSLagMaker().setAddQuarterOfYear(true);

 PrintStream stream = null;
List<List<NumericPrediction>> forecast = null;

try {            
      stream = new PrintStream("./path/forecast.txt");
      forecaster.buildForecaster(dataset, stream);
      forecaster.primeForecaster(dataset);
      forecast = forecaster.forecast(3, dataset, stream);        
 } catch (Exception e) {
       // TODO Auto-generated catch block
       e.printStackTrace();
}

// output the predictions
for (int i = 0; i < 3; i++) {
      List<NumericPrediction> predsAtStep = forecast.get(i);
       NumericPrediction predForTarget = predsAtStep.get(0);
       stream.print("" + predForTarget.predicted() + " ");
       stream.println();
}

The Java Code is hard to debug in webMethods, but it seems that
forecaster.buildForecaster(dataset, stream); is causing the Exception.

What am i missing?