Interface RandomVariable

    • Method Detail

      • equals

        boolean equals​(RandomVariable randomVariable)
        Compare this random variable with a given one
        Parameters:
        randomVariable - Random variable to compare with.
        Returns:
        True if this random variable and the given one are equal, otherwise false
      • getFiltrationTime

        double getFiltrationTime()
        Returns the filtration time.
        Returns:
        The filtration time.
      • getTypePriority

        int getTypePriority()
        Returns the type priority.
        Returns:
        The type priority.
        See Also:
        ssrn abstract 3246127
      • get

        double get​(int pathOrState)
        Evaluate at a given path or state.
        Parameters:
        pathOrState - Index of the path or state.
        Returns:
        Value of this random variable at the given path or state.
      • size

        int size()
        Returns the number of paths or states.
        Returns:
        Number of paths or states.
      • isDeterministic

        boolean isDeterministic()
        Check if this random variable is deterministic in the sense that it is represented by a single double value. Note that the methods returns false, if the random variable is represented by a vector where each element has the same value.
        Returns:
        True if this random variable is deterministic.
      • getValues

        default RandomVariable getValues()
        Returns the underlying values and a random variable. If the implementation supports an "inner representation", returns the inner representation. Otherwise just returns this.
        Returns:
        The underling values.
      • getRealizations

        double[] getRealizations()
        Returns a vector representing the realization of this random variable. This method is merely useful for analysis. Its interpretation depends on the context (Monte-Carlo or lattice). The method does not expose an internal data model.
        Returns:
        Vector of realizations of this random variable.
      • getOperator

        IntToDoubleFunction getOperator()
        Returns the operator path → this.get(path) corresponding to this random variable.
        Returns:
        The operator path → this.get(path) corresponding to this random variable.
      • getRealizationsStream

        DoubleStream getRealizationsStream()
        Returns a stream of doubles corresponding to the realizations of this random variable.
        Returns:
        A stream of doubles corresponding to the realizations of this random variable.
      • getMin

        double getMin()
        Returns the minimum value attained by this random variable.
        Returns:
        The minimum value.
      • getMax

        double getMax()
        Returns the maximum value attained by this random variable.
        Returns:
        The maximum value.
      • getAverage

        double getAverage()
        Returns the expectation of this random variable. The result of this method has to agrees with average().doubleValue().
        Returns:
        The average assuming equi-distribution.
      • getAverage

        double getAverage​(RandomVariable probabilities)
        Returns the expectation of this random variable for a given probability measure (weight). The result of this method is (mathematically) equivalent to
        this.mult(probabilities).getAverage() / probabilities.getAverage()
        while the internal implementation may differ, e.g. being more efficient by performing multiplication and summation in the same loop.
        Parameters:
        probabilities - The probability weights.
        Returns:
        The average assuming the given probability weights.
      • getVariance

        double getVariance()
        Returns the variance of this random variable, i.e., V where V = ((X-m)^2).getAverage() and X = this and m = X.getAverage().
        Returns:
        The average assuming equi-distribution.
      • getVariance

        double getVariance​(RandomVariable probabilities)
        Returns the variance of this random variable, i.e., V where V = ((X-m)^2).getAverage(probabilities) and X = this and m = X.getAverage(probabilities).
        Parameters:
        probabilities - The probability weights.
        Returns:
        The average assuming the given probability weights.
      • getSampleVariance

        double getSampleVariance()
        Returns the sample variance of this random variable, i.e., V * size()/(size()-1) where V = getVariance().
        Returns:
        The sample variance.
      • getStandardDeviation

        double getStandardDeviation()
        Returns the standard deviation of this random variable, i.e., sqrt(V) where V = ((X-m)^2).getAverage() and X = this and m = X.getAverage().
        Returns:
        The standard deviation assuming equi-distribution.
      • getStandardDeviation

        double getStandardDeviation​(RandomVariable probabilities)
        Returns the standard deviation of this random variable, i.e., sqrt(V) where V = ((X-m)^2).getAverage(probabilities) and X = this and m = X.getAverage(probabilities).
        Parameters:
        probabilities - The probability weights.
        Returns:
        The standard error assuming the given probability weights.
      • getStandardError

        double getStandardError()
        Returns the standard error (discretization error) of this random variable. For a Monte-Carlo simulation this is 1/Math.sqrt(n) * getStandardDeviation().
        Returns:
        The standard error assuming equi-distribution.
      • getStandardError

        double getStandardError​(RandomVariable probabilities)
        Returns the standard error (discretization error) of this random variable. For a Monte-Carlo simulation this is 1/Math.sqrt(n) * getStandardDeviation(RandomVariable).
        Parameters:
        probabilities - The probability weights.
        Returns:
        The standard error assuming the given probability weights.
      • getQuantile

        double getQuantile​(double quantile)
        Returns the quantile value for this given random variable, i.e., the value x such that P(this < x) = quantile, where P denotes the probability measure. The method will consider picewise constant values (with constant extrapolation) in the random variable. That is getQuantile(0) wiil return the smallest value and getQuantile(1) will return the largest value.
        Parameters:
        quantile - The quantile level.
        Returns:
        The quantile value assuming equi-distribution.
      • getQuantile

        double getQuantile​(double quantile,
                           RandomVariable probabilities)
        Returns the quantile value for this given random variable, i.e., the value x such that P(this < x) = quantile, where P denotes the probability measure.
        Parameters:
        quantile - The quantile level.
        probabilities - The probability weights.
        Returns:
        The quantile value assuming the given probability weights.
      • getQuantileExpectation

        double getQuantileExpectation​(double quantileStart,
                                      double quantileEnd)
        Returns the expectation over a quantile for this given random variable. The method will consider picewise constant values (with constant extrapolation) in the random variable. For a ≤ b the method returns (Σa ≤ i ≤ b x[i]) / (b-a+1), where
        • a = min(max((n+1) * quantileStart - 1, 0, 1);
        • b = min(max((n+1) * quantileEnd - 1, 0, 1);
        • n = this.size();
        For quantileStart > quantileEnd the method returns getQuantileExpectation(quantileEnd, quantileStart).
        Parameters:
        quantileStart - Lower bound of the integral.
        quantileEnd - Upper bound of the integral.
        Returns:
        The (conditional) expectation of the values between two quantile levels assuming equi-distribution.
      • getHistogram

        double[] getHistogram​(double[] intervalPoints)
        Generates a Histogram based on the realizations stored in this random variable. The returned result array's length is intervalPoints.length+1.
        • The value result[0] equals the relative frequency of values observed in the interval ( -infinity, intervalPoints[0] ].
        • The value result[i] equals the relative frequency of values observed in the interval ( intervalPoints[i-1], intervalPoints[i] ].
        • The value result[n] equals the relative frequency of values observed in the interval ( intervalPoints[n-1], infinity ).
        where n = intervalPoints.length. Note that the intervals are open on the left, closed on the right, i.e., result[i] contains the number of elements x with intervalPoints[i-1] < x ≤ intervalPoints[i]. Thus, is you have a random variable which only takes values contained in the (sorted) array possibleValues, then result = getHistogram(possibleValues) returns an array where result[i] is the relative frequency of occurrence of possibleValues[i]. The sum of result[i] over all i is equal to 1, except for uninitialized random variables where all values are 0.
        Parameters:
        intervalPoints - Array of ascending values defining the interval boundaries.
        Returns:
        A histogram with respect to a provided interval.
      • getHistogram

        double[][] getHistogram​(int numberOfPoints,
                                double standardDeviations)
        Generates a histogram based on the realizations stored in this random variable using interval points calculated from the arguments, see also getHistogram(double[]). The interval points are set with equal distance over an the interval of the specified standard deviation. The interval points used are x[i] = mean + alpha[i] * standardDeviations * sigma where The methods result is an array of two vectors, where result[0] are the intervals center points ('anchor points') and result[1] contains the relative frequency for the interval. The 'anchor point' for the interval (-infinity, x[0]) is x[0] - 1/2 (x[1]-x[0]) and the 'anchor point' for the interval (x[n], infinity) is x[n] + 1/2 (x[n]-x[n-1]). Here n = numberOfPoints is the number of interval points.
        Parameters:
        numberOfPoints - The number of interval points.
        standardDeviations - The number of standard deviations defining the discretization radius.
        Returns:
        A histogram, given as double[2][], where result[0] are the center point of the intervals and result[1] is the value of getHistogram(double[]) for the given the interval points. The length of result[0] and result[1] is numberOfPoints+1.
      • cache

        RandomVariable cache()
        Return a cacheable version of this object (often a self-reference). This method should be called when you store the object for later use, i.e., assign it, or when the object is consumed in a function, but later used also in another function.
        Returns:
        A cacheable version of this object (often a self-reference).
      • appy

        default RandomVariable appy​(RandomOperator operator)
        Applies x → operator(x) to this random variable. It returns a new random variable with the result.
        Parameters:
        operator - An unary operator/function, mapping RandomVariable to RandomVariable.
        Returns:
        New random variable with the result of the function.
      • apply

        RandomVariable apply​(DoubleUnaryOperator operator)
        Applies x → operator(x) to this random variable. It returns a new random variable with the result.
        Parameters:
        operator - An unary operator/function, mapping double to double.
        Returns:
        New random variable with the result of the function.
      • apply

        RandomVariable apply​(DoubleBinaryOperator operator,
                             RandomVariable argument)
        Applies x → operator(x,y) to this random variable, where x is this random variable and y is a given random variable. It returns a new random variable with the result.
        Parameters:
        operator - A binary operator/function, mapping (double,double) to double.
        argument - A random variable.
        Returns:
        New random variable with the result of the function.
      • apply

        RandomVariable apply​(DoubleTernaryOperator operator,
                             RandomVariable argument1,
                             RandomVariable argument2)
        Applies x → operator(x,y,z) to this random variable, where x is this random variable and y and z are given random variable. It returns a new random variable with the result.
        Parameters:
        operator - A ternary operator/function, mapping (double,double,double) to double.
        argument1 - A random variable representing y.
        argument2 - A random variable representing z.
        Returns:
        New random variable with the result of the function.
      • cap

        RandomVariable cap​(double cap)
        Applies x → min(x,cap) to this random variable. It returns a new random variable with the result.
        Parameters:
        cap - The cap.
        Returns:
        New random variable with the result of the function.
      • floor

        RandomVariable floor​(double floor)
        Applies x → max(x,floor) to this random variable. It returns a new random variable with the result.
        Parameters:
        floor - The floor.
        Returns:
        New random variable with the result of the function.
      • add

        RandomVariable add​(double value)
        Applies x → x + value to this random variable. It returns a new random variable with the result.
        Parameters:
        value - The value to add.
        Returns:
        New random variable with the result of the function.
      • sub

        RandomVariable sub​(double value)
        Applies x → x - value to this random variable.
        Parameters:
        value - The value to subtract.
        Returns:
        New random variable with the result of the function.
      • bus

        default RandomVariable bus​(double value)
        Applies x → value - x to this random variable.
        Parameters:
        value - The value from which this is subtracted.
        Returns:
        New random variable with the result of the function.
      • mult

        RandomVariable mult​(double value)
        Applies x → x * value to this random variable.
        Parameters:
        value - The value to multiply.
        Returns:
        New random variable with the result of the function.
      • div

        RandomVariable div​(double value)
        Applies x → x / value to this random variable.
        Parameters:
        value - The value to divide.
        Returns:
        New random variable with the result of the function.
      • vid

        default RandomVariable vid​(double value)
        Applies x → value / x to this random variable.
        Parameters:
        value - The numerator of the ratio where this is the denominator.
        Returns:
        New random variable with the result of the function.
      • pow

        RandomVariable pow​(double exponent)
        Applies x → pow(x,exponent) to this random variable.
        Parameters:
        exponent - The exponent.
        Returns:
        New random variable with the result of the function.
      • average

        RandomVariable average()
        Returns a random variable which is deterministic and corresponds the expectation of this random variable.
        Returns:
        New random variable being the expectation of this random variable.
      • expectation

        default RandomVariable expectation()
        Returns a random variable which is deterministic and corresponds the expectation of this random variable.
        Returns:
        New random variable being the expectation of this random variable.
      • variance

        default RandomVariable variance()
        Returns a random variable which is deterministic and corresponds the variance of this random variable.
        Returns:
        New random variable being the variance of this random variable and the argument.
      • covariance

        default RandomVariable covariance​(RandomVariable value)
        Returns a random variable which is deterministic and corresponds the covariance of this random variable and the argument.
        Parameters:
        value - The random variable Y to be used in Cov(X,Y) with X being this.
        Returns:
        New random variable being the covariance of this random variable and the argument.
      • getConditionalExpectation

        default RandomVariable getConditionalExpectation​(ConditionalExpectationEstimator conditionalExpectationOperator)
        Returns the conditional expectation using a given conditional expectation estimator.
        Parameters:
        conditionalExpectationOperator - A given conditional expectation estimator.
        Returns:
        The conditional expectation of this random variable (as a random variable)
      • squared

        RandomVariable squared()
        Applies x → x * x to this random variable.
        Returns:
        New random variable with the result of the function.
      • sqrt

        RandomVariable sqrt()
        Applies x → sqrt(x) to this random variable.
        Returns:
        New random variable with the result of the function.
      • exp

        RandomVariable exp()
        Applies x → exp(x) to this random variable.
        Returns:
        New random variable with the result of the function.
      • expm1

        default RandomVariable expm1()
        Applies x → expm1(x) (that is x → exp(x)-1.0) to this random variable.
        Returns:
        New random variable with the result of the function.
      • log

        RandomVariable log()
        Applies x → log(x) to this random variable.
        Returns:
        New random variable with the result of the function.
      • sin

        RandomVariable sin()
        Applies x → sin(x) to this random variable.
        Returns:
        New random variable with the result of the function.
      • cos

        RandomVariable cos()
        Applies x → cos(x) to this random variable.
        Returns:
        New random variable with the result of the function.
      • add

        RandomVariable add​(RandomVariable randomVariable)
        Applies x → x+randomVariable to this random variable.
        Parameters:
        randomVariable - A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • sub

        RandomVariable sub​(RandomVariable randomVariable)
        Applies x → x-randomVariable to this random variable.
        Parameters:
        randomVariable - A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • bus

        RandomVariable bus​(RandomVariable randomVariable)
        Applies x → randomVariable-x to this random variable.
        Parameters:
        randomVariable - A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • mult

        RandomVariable mult​(RandomVariable randomVariable)
        Applies x → x*randomVariable to this random variable.
        Parameters:
        randomVariable - A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • div

        RandomVariable div​(RandomVariable randomVariable)
        Applies x → x/randomVariable to this random variable.
        Parameters:
        randomVariable - A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • vid

        RandomVariable vid​(RandomVariable randomVariable)
        Applies x → randomVariable/x to this random variable.
        Parameters:
        randomVariable - A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • cap

        RandomVariable cap​(RandomVariable cap)
        Applies x → min(x,cap) to this random variable.
        Parameters:
        cap - The cap. A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • floor

        RandomVariable floor​(RandomVariable floor)
        Applies x → max(x,floor) to this random variable.
        Parameters:
        floor - The floor. A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • accrue

        RandomVariable accrue​(RandomVariable rate,
                              double periodLength)
        Applies x → x * (1.0 + rate * periodLength) to this random variable.
        Parameters:
        rate - The accruing rate. A random variable (compatible with this random variable).
        periodLength - The period length
        Returns:
        New random variable with the result of the function.
      • discount

        RandomVariable discount​(RandomVariable rate,
                                double periodLength)
        Applies x → x / (1.0 + rate * periodLength) to this random variable.
        Parameters:
        rate - The discounting rate. A random variable (compatible with this random variable).
        periodLength - The period length
        Returns:
        New random variable with the result of the function.
      • choose

        RandomVariable choose​(RandomVariable valueIfTriggerNonNegative,
                              RandomVariable valueIfTriggerNegative)
        Applies x → (x ≥ 0 ? valueIfTriggerNonNegative : valueIfTriggerNegative)
        Parameters:
        valueIfTriggerNonNegative - The value used if this is greater or equal 0
        valueIfTriggerNegative - The value used if the this is less than 0
        Returns:
        New random variable with the result of the function.
      • invert

        RandomVariable invert()
        Applies x → 1/x to this random variable.
        Returns:
        New random variable with the result of the function.
      • abs

        RandomVariable abs()
        Applies x → Math.abs(x), i.e. x → |x| to this random variable.
        Returns:
        New random variable with the result of the function.
      • addProduct

        RandomVariable addProduct​(RandomVariable factor1,
                                  double factor2)
        Applies x → x + factor1 * factor2
        Parameters:
        factor1 - The factor 1. A random variable (compatible with this random variable).
        factor2 - The factor 2.
        Returns:
        New random variable with the result of the function.
      • addProduct

        RandomVariable addProduct​(RandomVariable factor1,
                                  RandomVariable factor2)
        Applies x → x + factor1 * factor2
        Parameters:
        factor1 - The factor 1. A random variable (compatible with this random variable).
        factor2 - The factor 2. A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • addRatio

        RandomVariable addRatio​(RandomVariable numerator,
                                RandomVariable denominator)
        Applies x → x + numerator / denominator
        Parameters:
        numerator - The numerator of the ratio to add. A random variable (compatible with this random variable).
        denominator - The denominator of the ratio to add. A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • subRatio

        RandomVariable subRatio​(RandomVariable numerator,
                                RandomVariable denominator)
        Applies x → x - numerator / denominator
        Parameters:
        numerator - The numerator of the ratio to sub. A random variable (compatible with this random variable).
        denominator - The denominator of the ratio to sub. A random variable (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • addSumProduct

        default RandomVariable addSumProduct​(RandomVariable[] factor1,
                                             RandomVariable[] factor2)
        Applies \( x \mapsto x + \sum_{i=0}^{n-1} factor1_{i} * factor2_{i}
        Parameters:
        factor1 - The factor 1. A list of random variables (compatible with this random variable).
        factor2 - The factor 2. A list of random variables (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • addSumProduct

        default RandomVariable addSumProduct​(List<RandomVariable> factor1,
                                             List<RandomVariable> factor2)
        Applies \( x \mapsto x + \sum_{i=0}^{n-1} factor1_{i} * factor2_{i}
        Parameters:
        factor1 - The factor 1. A list of random variables (compatible with this random variable).
        factor2 - The factor 2. A list of random variables (compatible with this random variable).
        Returns:
        New random variable with the result of the function.
      • isNaN

        RandomVariable isNaN()
        Applies x → (Double.isNaN(x) ? 1.0 : 0.0)
        Returns:
        A random variable which is 1.0 for all states that are NaN, otherwise 0.0.