# gauss

This script returns a pseudo-random number with Gaussian or normal distribution, meaning the values returned tend to cluster around a given average or mean value. This could be useful if one needed a random behavior or outcome where deviations from the desired target become more rare as the magnitude of the deviation increases.

An example use might be an enemy AI whose skill is represented by the
degree of error in its aiming ability. If a target is at 90 degrees,
`aim = gauss(90,5)`

would return a firing direction with a small degree
of error. This degree of error (or deviation) is controlled by the second
argument. In this case, the value returned would be within 5 degrees
(one standard deviation) of the desired direction (the mean) about 68% of
the time, and within 10 degrees (two standard deviations) about 95% of the
time. The lower the given deviation, the greater chance the returned value
will be near the given mean, and the more accurate the aim of the AI would be.

From the Wikipedia entry on normal distribution:

In probability theory, the

normal(orGaussian)distributionis a continuous probability distribution that is often used as a first approximation to describe real-valued random variables that tend to cluster around a single mean value. The graph of the associated probability density function is "bell"-shaped, and is known as theGaussian functionorbell curve:$$f(x) = \frac{1}{\sqrt{2\pi\sigma^2}} e^{ -\frac{(x-\mu)^2}{2\sigma^2} }$$

where parameter \(\mu\) is the mean (location of the peak) and \(\sigma^2\) is the variance (the measure of the width of the distribution). The distribution with \(\mu = 0\) and \(\sigma^2 = 1\) is called the

standard normal.

- gauss(m, sd)
- Returns a pseudo-random number with an exact Gaussian distribution.

`COPY````
/// @func gauss(m, sd)
///
/// @desc Returns a pseudo-random number with an exact Gaussian distribution.
///
/// @param {real} m mean value of the distribution
/// @param {real} sd standard deviation of distribution
///
/// @return {real} random number with Gaussian distribution
///
/// GMLscripts.com/license
function gauss(m, sd)
{
var x1, x2, w;
do {
x1 = random(2) - 1;
x2 = random(2) - 1;
w = x1 * x1 + x2 * x2;
} until (0 < w && w < 1);
w = sqrt(-2 * ln(w) / w);
return m + sd * x1 * w;
}
```

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