GRASS 8 Programmer's Manual 8.5.0(2026)-8d6ceba290
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xgraph.c
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1#include <stdlib.h>
2
3#include <grass/gis.h>
4#include <grass/raster.h>
5#include <grass/calc.h>
6
7/****************************************************************
8graph(x, x1,y1, x2,y2, ... xn,yn) returns y value based on graph
9described by the x,y pairs.
10****************************************************************/
11
12int c_graph(int argc, int *argt)
13{
14 int i;
15
16 if (argc < 3)
17 return E_ARG_LO;
18
19 if (argc % 2 == 0)
20 return E_ARG_NUM;
21
22 for (i = 0; i <= argc; i++)
23 argt[i] = DCELL_TYPE;
24
25 return 0;
26}
27
28int f_graph(int argc, const int *argt, void **args)
29{
30 DCELL **argz = (DCELL **)args;
31 DCELL *res = argz[0];
32 int n = (argc - 1) / 2;
33 int i, j;
34
35 if (argc < 3)
36 return E_ARG_LO;
37
38 if (argc % 2 == 0)
39 return E_ARG_NUM;
40
41 if (argt[0] != DCELL_TYPE)
42 return E_RES_TYPE;
43
44 for (i = 1; i <= argc; i++)
45 if (argt[i] != DCELL_TYPE)
46 return E_ARG_TYPE;
47
48 for (i = 0; i < columns; i++) {
49#define X(j) (argz[2 + 2 * (j) + 0][i])
50#define Y(j) (argz[2 + 2 * (j) + 1][i])
51#define x (argz[1][i])
52
53 if (IS_NULL_D(&x))
54 goto null;
55
56 for (j = 0; j < n; j++)
57 if (IS_NULL_D(&X(j)))
58 goto null;
59
60 for (j = 0; j < n - 1; j++)
61 if (X(j + 1) <= X(j))
62 goto null;
63
64 if (x <= X(0)) {
65 if (IS_NULL_D(&Y(0)))
66 goto null;
67 res[i] = Y(0);
68 continue;
69 }
70
71 if (x >= X(n - 1)) {
72 if (IS_NULL_D(&Y(n - 1)))
73 goto null;
74 res[i] = Y(n - 1);
75 continue;
76 }
77
78 for (j = 0; j < n - 1; j++) {
79 if (x > X(j + 1))
80 continue;
81
82 if (IS_NULL_D(&Y(j)) || IS_NULL_D(&Y(j + 1)))
83 goto null;
84
85 res[i] = Y(j) + (x - X(j)) * (Y(j + 1) - Y(j)) / (X(j + 1) - X(j));
86
87 break;
88 }
89#undef X
90#undef Y
91#undef x
92
93 continue;
94
95 null:
96 SET_NULL_D(&res[i]);
97 }
98
99 return 0;
100}
101
102int f_graph2(int argc, const int *argt, void **args)
103{
104 DCELL **argz = (DCELL **)args;
105 DCELL *res = argz[0];
106 int n = (argc - 1) / 2;
107 int i, j;
108
109 if (argc < 3)
110 return E_ARG_LO;
111
112 if (argc % 2 == 0)
113 return E_ARG_NUM;
114
115 if (argt[0] != DCELL_TYPE)
116 return E_RES_TYPE;
117
118 for (i = 1; i <= argc; i++)
119 if (argt[i] != DCELL_TYPE)
120 return E_ARG_TYPE;
121
122 for (i = 0; i < columns; i++) {
123#define X(j) (argz[2 + (j) + 0][i])
124#define Y(j) (argz[2 + (j) + n][i])
125#define x (argz[1][i])
126
127 if (IS_NULL_D(&x))
128 goto null;
129
130 for (j = 0; j < n; j++)
131 if (IS_NULL_D(&X(j)))
132 goto null;
133
134 for (j = 0; j < n - 1; j++)
135 if (X(j + 1) <= X(j))
136 goto null;
137
138 if (x <= X(0)) {
139 if (IS_NULL_D(&Y(0)))
140 goto null;
141 res[i] = Y(0);
142 continue;
143 }
144
145 if (x >= X(n - 1)) {
146 if (IS_NULL_D(&Y(n - 1)))
147 goto null;
148 res[i] = Y(n - 1);
149 continue;
150 }
151
152 for (j = 0; j < n - 1; j++) {
153 if (x > X(j + 1))
154 continue;
155
156 if (IS_NULL_D(&Y(j)) || IS_NULL_D(&Y(j + 1)))
157 goto null;
158
159 res[i] = Y(j) + (x - X(j)) * (Y(j + 1) - Y(j)) / (X(j + 1) - X(j));
160
161 break;
162 }
163#undef X
164#undef Y
165#undef x
166
167 continue;
168
169 null:
170 SET_NULL_D(&res[i]);
171 }
172
173 return 0;
174}
columns
int columns
Definition calc.c:11
X
#define X(j)
f_graph2
int f_graph2(int argc, const int *argt, void **args)
Definition xgraph.c:102
x
#define x
f_graph
int f_graph(int argc, const int *argt, void **args)
Definition xgraph.c:28
c_graph
int c_graph(int argc, int *argt)
Definition xgraph.c:12
Y
#define Y(j)