I am new to ECJ and I am trying to use the system as a librarary for 
symbolic regression of data points with multiple independent variables.  
I have followed the tutorial 4 and built the X, Y, DoubleData and 
MultipleRegression classes.  What I am not sure about is whether each 
independent variable needs a class representation or is the X class 
enhanced to include properties for each variable such that 
instanceX.x1...xn?  Also, I am using JNBridge to access ECJ via C#.  
Sample code below:  

public void Run(RaptorDataSet trainingSet,
                      RaptorDataSet testingSet,
                      RaptorPlugInParameters parameters)
            SimpleEvolutionState evoState = new SimpleEvolutionState();
            //ensure that seed is different for each run
            evoState.randomSeedOffset = new Random
            //set user defined parameters
            evoState.breedthreads = this.GetThrdsForBreeding(parameters);
            evoState.evalthreads = this.GetThrdsEvaluation(parameters);  
            evoState.numGenerations = this.GetNumGen(parameters);
            evoState.quitOnRunComplete = this.QuitOnComplete
            //initialize population TBD
            //run problem TBD           
            //clean up