package sansmodels;

public class PowerLaw extends SANSModel{
 
    private double coeff, power, background;

    //Default constructor
    public PowerLaw() {
        coeff = 1.0e-6;
        power = 4.0;
        background = 0.0;
        setNumberOfParameters(3);
        String[] parameters = {"Coefficient, A", "(-)Power",
            "Background (cm-1)"};
        setParametersText(parameters);
    }

    public PowerLaw(double inCoeff, double inPower,
                  double inBackground) {
        coeff = inCoeff; 
        power = inPower;
        background = inBackground;
        setNumberOfParameters(3);
        String[] parameters = {"Scale", "Correlation Length (A)",
            "Background (cm-1)"};
        setParametersText(parameters);
    }

    public double getFormFactor(double inX) {
        return coeff*Math.pow(inX,-1.0*power)
            *getStructureFactor().calculate(inX) + background;
    }

    public void setParameters(double[] inParameters) {
        coeff = inParameters[0];
        power = inParameters[1];
        background = inParameters[2];
    }
 
    public double[] getParameters() {
        double[] outParameters = new double[3];
        outParameters[0] = coeff;
        outParameters[1] = power;
        outParameters[2] = background;
        return outParameters;
    }
}