GRASS GIS 8 Programmer's Manual 8.2.0(2022)-exported
xatan.c
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1
2#include <stdlib.h>
3#include <math.h>
4
5#include <grass/gis.h>
6#include <grass/raster.h>
7#include <grass/calc.h>
8
9/**********************************************************************
10atan(x) range [-90,90]
11atan(x,y) = atan(y/x) range[0,360]
12
13 if floating point exception occurs during the evaluation of atan(x)
14 the result is NULL
15
16 note: result is in degrees
17**********************************************************************/
18
19#define RADIANS_TO_DEGREES (180.0 / M_PI)
20
21int f_atan(int argc, const int *argt, void **args)
22{
23 DCELL *res = args[0];
24 DCELL *arg1 = args[1];
25 DCELL *arg2;
26 int i;
27
28 if (argc < 1)
29 return E_ARG_LO;
30 if (argc > 2)
31 return E_ARG_HI;
32
33 if (argt[0] != DCELL_TYPE)
34 return E_RES_TYPE;
35
36 if (argt[1] != DCELL_TYPE)
37 return E_ARG_TYPE;
38
39 if (argc > 1 && argt[2] != DCELL_TYPE)
40 return E_ARG_TYPE;
41
42 arg2 = (argc > 1) ? args[2] : NULL;
43
44 for (i = 0; i < columns; i++)
45 if (IS_NULL_D(&arg1[i]))
46 SET_NULL_D(&res[i]);
47 else if (argc > 1 && IS_NULL_D(&arg2[i]))
48 SET_NULL_D(&res[i]);
49
50 else {
52 if (argc == 1)
53 res[i] = RADIANS_TO_DEGREES * atan(arg1[i]);
54 else {
55 res[i] = RADIANS_TO_DEGREES * atan2(arg2[i], arg1[i]);
56 if (res[i] < 0)
57 res[i] += 360.0;
58 }
60 SET_NULL_D(&res[i]);
61 }
62
63 return 0;
64}
volatile int floating_point_exception
Definition: calc.c:9
int columns
Definition: calc.c:12
#define NULL
Definition: ccmath.h:32
#define RADIANS_TO_DEGREES
Definition: xatan.c:19
int f_atan(int argc, const int *argt, void **args)
Definition: xatan.c:21