GRASS GIS 8 Programmer's Manual  8.4.0dev(2024)-535c39c9fc
gauss.c
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1 #include <math.h>
2 #include <grass/gmath.h>
3 
4 /*!
5  * \fn double G_math_rand_gauss(const int seed, const double sigma)
6  *
7  * \brief Gaussian random number generator
8  *
9  * Gaussian random number generator (mean = 0.0)
10  *
11  * \param[in] seed
12  & \param[in] sigma
13  * \return double
14  */
15 
16 double G_math_rand_gauss(double sigma)
17 {
18  double x, y, r2;
19 
20  do {
21  /* choose x,y in uniform square (-1,-1) to (+1,+1) */
22  x = -1 + 2 * G_math_rand();
23  y = -1 + 2 * G_math_rand();
24 
25  /* see if it is in the unit circle */
26  r2 = x * x + y * y;
27  } while (r2 > 1.0 || r2 == 0);
28 
29  /* Box-Muller transform */
30  return sigma * y * sqrt(-2.0 * log(r2) / r2);
31 }
float G_math_rand(void)
Definition: rand1.c:16
double G_math_rand_gauss(double sigma)
Definition: gauss.c:16
#define x