/**
* As described by Bernt Arne Ødegaard in Financial Numerical Recipes in C++.
*
* <p>Returns P(X < a, Y < b) where X, Y are gaussian random variables N(0, 1) of the bivariate
* normal distribution with correlation c in [-1, 1] between X and Y.
*/
public static double cdf(double a, double b, double c) {
if (a == Double.NaN || b == Double.NaN || c == Double.NaN) {
throw new IllegalArgumentException("Arguments must be a number.");
}
if (a == Double.NaN) {
System.out.println("");
}
a = handleInfinity(a);
b = handleInfinity(b);
c = handleInfinity(c);
if (a == Double.NaN) {
System.out.println("");
}
if (a <= 0 && b <= 0 && c <= 0) {
final double aprime = a / FastMath.sqrt(2d * (1d - c * c));
final double bprime = b / FastMath.sqrt(2d * (1d - c * c));
double sum = 0;
for (int i = 0; i < A.length; i++) {
for (int j = 0; j < A.length; j++) {
sum += A[i] * A[j] * f(B[i], B[j], aprime, bprime, c);
}
}
sum *= FastMath.sqrt(1d - c * c) / FastMath.PI;
return sum;
}
// a or b may be too big and their multiplication may result in NaN.
if (c * a * b
<= 0) { // c is smaller (between [-1, 1]) and will help to avoid NaNs. So we multiply c
// first.
if ((a <= 0) && (b >= 0) && (c >= 0)) {
return normal.cumulativeProbability(a) - cdf(a, -b, -c);
} else if ((a >= 0) && (b <= 0) && (c >= 0)) {
return normal.cumulativeProbability(b) - cdf(-a, b, -c);
} else if ((a >= 0) && (b >= 0) && (c <= 0)) {
return normal.cumulativeProbability(a)
+ normal.cumulativeProbability(b)
- 1
+ cdf(-a, -b, c);
}
} else if (c * a * b >= 0) {
final double denum = FastMath.sqrt(a * a - 2d * c * a * b + b * b);
final double rho1 = ((c * a - b) * FastMath.signum(a)) / denum;
final double rho2 = ((c * b - a) * FastMath.signum(b)) / denum;
final double delta = (1d - FastMath.signum(a) * FastMath.signum(b)) / 4d;
return cdf(a, 0, rho1) + cdf(b, 0, rho2) - delta;
}
throw new RuntimeException(
"Should never get here. Values of [a; b ; c] = [" + a + "; " + b + "; " + c + "].");
}
@Override
protected OperationData process(IDataset input, IMonitor monitor) {
double theta = 0;
try {
theta = ScanMetadata.getTheta(input);
} catch (Exception e) {
}
NormalDistribution beamfootprint =
new NormalDistribution(
0, (1e-3 * model.getBeamHeight() / 2 * Math.sqrt(2 * Math.log(2) - 0.5)));
double areaCorrection =
2
* (beamfootprint.cumulativeProbability(
(model.getFootprint()
* Math.sin((theta + model.getAngularFudgeFactor()) * Math.PI / 180))));
Dataset output = DatasetUtils.cast(input, Dataset.FLOAT64);
output = Maths.multiply(input, areaCorrection);
Dataset outputSum =
DatasetFactory.createFromObject((DatasetUtils.cast(output, Dataset.FLOAT64)).sum());
return new OperationData(output, outputSum);
}
@Test
/** Test of integrator for the sine function. */
public void testSinFunction() {
UnivariateFunction f = new Gaussian(10, 2);
UnivariateIntegrator integrator = new SimpsonIntegrator();
double a, b, expected, tolerance, result;
a = 8;
b = 12;
expected = 0.68269;
tolerance = 0.00001;
tolerance = Math.abs(expected * integrator.getRelativeAccuracy());
result = integrator.integrate(MAX_EVAL, f, a, b);
assertEquals(expected, result, tolerance);
log.info(
"Result: "
+ result
+ ", tolerance: "
+ tolerance
+ " - Relative accuracy: "
+ integrator.getRelativeAccuracy()
+ " - Absolute accuracy: "
+ integrator.getAbsoluteAccuracy()
+ " - Iterations: "
+ integrator.getIterations());
NormalDistribution distribution = new NormalDistribution(10, 2);
result = distribution.cumulativeProbability(a, b);
log.info("Distribution result: " + result);
}
// Model "a" with a normal distribution, and test whether cdf(mean(b)) > pvalue
public boolean significantIncrease(List<Double> a, List<Double> b, double pvalue) {
double meanA = mean(a);
double sd = 0;
for (Double val : a) {
sd += (val - meanA) * (val - meanA);
}
sd = Math.sqrt(sd / (a.size() - 1));
if (sd <= 0) {
return true;
}
double meanB = mean(b);
NormalDistribution dist = new NormalDistribution(meanA, sd);
double p = dist.cumulativeProbability(meanB);
boolean significant = (p > pvalue);
System.out.println("p-value=" + p + ", " + (significant ? "increase" : "no increase"));
return significant;
}
public static double normalCDF(double x, double mean, double sigma) {
NormalDistribution normDist = new NormalDistribution(mean, sigma);
double ret = normDist.cumulativeProbability(x);
return ret;
}
