Random.NextGaussian Method

  • Reference

Definition

Namespace:
Java.Util
Assembly:
Mono.Android.dll

Returns the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence.

[Android.Runtime.Register("nextGaussian", "()D", "GetNextGaussianHandler")]
public virtual double NextGaussian ();
[<Android.Runtime.Register("nextGaussian", "()D", "GetNextGaussianHandler")>]
abstract member NextGaussian : unit -> double
override this.NextGaussian : unit -> double

Returns

Double

the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence

Attributes
RegisterAttribute

Remarks

Returns the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0 from this random number generator's sequence.

The general contract of nextGaussian is that one double value, chosen from (approximately) the usual normal distribution with mean 0.0 and standard deviation 1.0, is pseudorandomly generated and returned.

The method nextGaussian is implemented by class Random as if by a threadsafe version of the following:

{@code
            private double nextNextGaussian;
            private boolean haveNextNextGaussian = false;

            public double nextGaussian() {
              if (haveNextNextGaussian) {
                haveNextNextGaussian = false;
                return nextNextGaussian;
              } else {
                double v1, v2, s;
                do {
                  v1 = 2 * nextDouble() - 1;   // between -1.0 and 1.0
                  v2 = 2 * nextDouble() - 1;   // between -1.0 and 1.0
                  s = v1 * v1 + v2 * v2;
                } while (s >= 1 || s == 0);
                double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s);
                nextNextGaussian = v2 * multiplier;
                haveNextNextGaussian = true;
                return v1 * multiplier;
              }
            }}

This uses the polar method of G. E. P. Box, M. E. Muller, and G. Marsaglia, as described by Donald E. Knuth in The Art of Computer Programming, Volume 2: Seminumerical Algorithms, section 3.4.1, subsection C, algorithm P. Note that it generates two independent values at the cost of only one call to StrictMath.log and one call to StrictMath.sqrt.

Java documentation for java.util.Random.nextGaussian().

Portions of this page are modifications based on work created and shared by the Android Open Source Project and used according to terms described in the Creative Commons 2.5 Attribution License.

Applies to