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Learning Mixture of Gamma Distribution RRS feed

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    Hi, Infer.net people,

            I cant get rid of a exception(due to Factor.Difference) for implementing two mixtures of Gamma.  The code is below, and I want to estimate the rate parameter, and the data is generated by two gamma distribution , which is mirror to each other. I have tried all 3 inference algorithms.

    Thank you for the help.

                double[] data = new double[100];
            double shape = 2;
            double rate = 0.5;
            for (int i = 0; i < data.Length; i++) data[i] = Math.Pow(-1,i)*Rand.Gamma(shape) / rate;
            var rateRandV = Variable.Random<double>(Gamma.Uniform());// Variable.GammaFromMeanAndVariance(rate * 2, 10);
            

            for (int i = 0; i < data.Length; i++)
            {
                var Z = Variable.Bernoulli(0.5);
                Variable<double> x;
                using(Variable.If(Z))
                {
                    x = Variable.GammaFromShapeAndRate(shape, rateRandV);
                }
                using (Variable.IfNot(Z))
                {
                    x = -Variable.GammaFromShapeAndRate(shape, rateRandV);
                }
                x.ObservedValue = data[i];
            }
            InferenceEngine engine = new InferenceEngine(new VariationalMessagePassing());
            Console.WriteLine("rate=" + engine.Infer(rateRandV));

    Friday, October 24, 2014 8:46 PM

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    Try using SetTo inside the conditionals, as explained here. For how to work with arrays and ranges, look here. For a solution to a similar problem, look here. 

    Friday, October 24, 2014 10:24 PM
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    Thanks for the reply.  But the exception is not due to the SetTo Issue. And it is a compile fail.

    Error 0: This model is not supported with VariationalMessagePassing due to Factor.Difference(double difference, double a, double b). Try using a different algorithm or expressing the model differently in

    Factor.Difference(0.0, vdouble5_use)

    Details: [0] System.ArgumentException: Gamma is not assignable from Gaussian for result of method DoubleMinusVmpOp.BAverageLogarithm 

      // Sample data from standard Gaussian
            double[] data = new double[100];
            double shape = 2;
            double rate = 0.5;
            for (int i = 0; i < data.Length; i++) data[i] = Math.Pow(-1,i)*Rand.Gamma(shape) / rate;
            var rateRandV = Variable.Random<double>(Gamma.Uniform()); 
            

            for (int i = 0; i < data.Length; i++)
            {
                var Z = Variable.Bernoulli(0.5);
                Variable<double> x = Variable.New<double>();
                using(Variable.If(Z))
                {
                    x.SetTo(Variable.GammaFromShapeAndRate(shape, rateRandV));
                }
                using (Variable.IfNot(Z))
                {
                     x.SetTo( -Variable.GammaFromShapeAndRate(shape, rateRandV));
                }
                x.ObservedValue = data[i];
            }
            InferenceEngine engine = new InferenceEngine(new VariationalMessagePassing());
            Console.WriteLine("rate=" + engine.Infer(rateRandV));

    Saturday, October 25, 2014 1:12 AM
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    Negating a Gamma variable is not supported.
    Saturday, October 25, 2014 11:53 AM
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