GRASS GIS 7 Programmer's Manual  7.7.svn(2018)-r73378
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var.c
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1 #include <math.h>
2 #include <grass/imagery.h>
3 /* sum: sum of x
4  * sum2: sum of x squared
5  * n: number of points
6  */
7 
8 double I_variance(double sum, double sum2, int n)
9 {
10  if (n < 2)
11  return ((double)0.0);
12  else
13  return ((sum2 - sum * sum / n) / (n - 1));
14 }
15 
16 double I_stddev(double sum, double sum2, int n)
17 {
18  if (n < 2)
19  return ((double)-99.0);
20  else
21  return sqrt(I_variance(sum, sum2, n));
22 }
double I_stddev(double sum, double sum2, int n)
Definition: var.c:16
double I_variance(double sum, double sum2, int n)
Definition: var.c:8