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JSci is a set of open source Java packages. The aim is to encapsulate scientific methods/principles in the most natural way possible. As such they should greatly aid the development of scientific based software.
It offers: abstract math interfaces, linear algebra (support for various matrix and vector types), statistics (including probability distributions), wavelets, newtonian mechanics, chart/graph components (AWT and Swing), MathML DOM implementation, ...
Note: some packages, like javax.comm, for the astro and instruments package aren't listed as dependencies (not available).
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package JSci.maths.statistics;
/**
* The GeometricDistribution class provides an object for encapsulating geometric distributions.
* @version 0.2
* @author Mark Hale
*/
public final class GeometricDistribution extends ProbabilityDistribution {
private double success;
private double failure;
/**
* Constructs a geometric distribution.
* @param prob the probability of success.
*/
public GeometricDistribution(double prob) {
if(prob<0.0 || prob>1.0)
throw new OutOfRangeException("The probability should be between 0.0 and 1.0.");
success=prob;
failure=1.0-prob;
}
/**
* Returns the success parameter.
*/
public double getSuccessParameter() {
return success;
}
/**
* Returns the mean.
*/
public double getMean() {
return 1.0/success;
}
/**
* Returns the variance.
*/
public double getVariance() {
return failure/(success*success);
}
/**
* Probability density function of a geometric distribution.
* P(X) = p (1-p)X-1.
* @param X should be integer-valued.
* @return the probability that a stochastic variable x has the value X, i.e. P(x=X).
*/
public double probability(double X) {
checkRange(X,0.0,Double.MAX_VALUE);
return success*Math.pow(failure,X-1);
}
/**
* Cumulative geometric distribution function.
* @param X should be integer-valued.
* @return the probability that a stochastic variable x is less than or equal to X, i.e. P(x<=X).
*/
public double cumulative(double X) {
checkRange(X,0.0,Double.MAX_VALUE);
return 1.0-Math.pow(failure,X);
}
/**
* Inverse of the cumulative geometric distribution function.
* @return the value X for which P(x<=X).
*/
public double inverse(double probability) {
checkRange(probability);
return Math.log(1.0-probability)/Math.log(failure);
}
}