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xmedian.c
Go to the documentation of this file.
#include <stdlib.h>
#include <stdbool.h>
#include <grass/gis.h>
#include <grass/raster.h>
#include <grass/calc.h>
/**********************************************************************
median(x1,x2,..,xn)
return median of arguments
**********************************************************************/
#define SIZE_THRESHOLD 32
static int icmp(const void *aa, const void *bb)
{
const CELL *a = aa;
const CELL *b = bb;
return *a - *b;
}
static int fcmp(const void *aa, const void *bb)
{
const FCELL *a = aa;
const FCELL *b = bb;
if (*a < *b)
return -1;
if (*a > *b)
return 1;
return 0;
}
static int dcmp(const void *aa, const void *bb)
{
const DCELL *a = aa;
const DCELL *b = bb;
if (*a < *b)
return -1;
if (*a > *b)
return 1;
return 0;
}
int f_median(int argc, const int *argt, void **args)
{
int size = argc * Rast_cell_size(argt[0]);
int i, j;
bool use_heap = false;
if (argc < 1)
return E_ARG_LO;
for (i = 1; i <= argc; i++)
if (argt[i] != argt[0])
return E_ARG_TYPE;
switch (argt[0]) {
case CELL_TYPE: {
CELL stack_array[SIZE_THRESHOLD];
CELL *a = stack_array;
if (argc > SIZE_THRESHOLD) {
a = G_malloc(size);
use_heap = true;
}
CELL *res = args[0];
CELL **argv = (CELL **)&args[1];
CELL *a1 = &a[(argc - 1) / 2];
CELL *a2 = &a[argc / 2];
for (i = 0; i < columns; i++) {
int nv = 0;
for (j = 0; j < argc && !nv; j++) {
if (IS_NULL_C(&argv[j][i]))
nv = 1;
else
a[j] = argv[j][i];
}
if (nv)
SET_NULL_C(&res[i]);
else {
qsort(a, argc, sizeof(CELL), icmp);
res[i] = (*a1 + *a2) / 2;
}
}
if (use_heap) {
G_free(a);
}
return 0;
}
case FCELL_TYPE: {
FCELL stack_array[SIZE_THRESHOLD];
FCELL *a = stack_array;
if (argc > SIZE_THRESHOLD) {
a = G_malloc(size);
use_heap = true;
}
FCELL *res = args[0];
FCELL **argv = (FCELL **)&args[1];
FCELL *a1 = &a[(argc - 1) / 2];
FCELL *a2 = &a[argc / 2];
for (i = 0; i < columns; i++) {
int nv = 0;
for (j = 0; j < argc && !nv; j++) {
if (IS_NULL_F(&argv[j][i]))
nv = 1;
else
a[j] = argv[j][i];
}
if (nv)
SET_NULL_F(&res[i]);
else {
qsort(a, argc, sizeof(FCELL), fcmp);
res[i] = (*a1 + *a2) / 2;
}
}
if (use_heap) {
G_free(a);
}
return 0;
}
case DCELL_TYPE: {
DCELL stack_array[SIZE_THRESHOLD];
DCELL *a = stack_array;
if (argc > SIZE_THRESHOLD) {
a = G_malloc(size);
use_heap = true;
}
DCELL *res = args[0];
DCELL **argv = (DCELL **)&args[1];
DCELL *a1 = &a[(argc - 1) / 2];
DCELL *a2 = &a[argc / 2];
for (i = 0; i < columns; i++) {
int nv = 0;
for (j = 0; j < argc && !nv; j++) {
if (IS_NULL_D(&argv[j][i]))
nv = 1;
else
a[j] = argv[j][i];
}
if (nv)
SET_NULL_D(&res[i]);
else {
qsort(a, argc, sizeof(DCELL), dcmp);
res[i] = (*a1 + *a2) / 2;
}
}
if (use_heap) {
G_free(a);
}
return 0;
}
default:
return E_INV_TYPE;
}
}
G_free
void G_free(void *buf)
Free allocated memory.
Definition alloc.c:147
columns
int columns
Definition calc.c:11
b
double b
Definition driver/set_window.c:5
f_median
int f_median(int argc, const int *argt, void **args)
Definition xmedian.c:47
SIZE_THRESHOLD
#define SIZE_THRESHOLD
Definition xmedian.c:13