xnmedian.c

Go to the documentation of this file.

#include <stdlib.h>

#include <grass/gis.h>
#include <grass/raster.h>
#include <grass/raster.h>
#include <grass/calc.h>

/**********************************************************************
median(x1,x2,..,xn)
   return median of arguments
**********************************************************************/

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_nmedian(int argc, const int *argt, void **args)
{
    static void *array;
    static int alloc;
    int size = argc * Rast_cell_size(argt[0]);
    int i, j;

    if (argc < 1)
        return E_ARG_LO;

    for (i = 1; i <= argc; i++)
        if (argt[i] != argt[0])
            return E_ARG_TYPE;

    if (size > alloc) {
        alloc = size;
        array = G_realloc(array, size);
    }

    switch (argt[0]) {
    case CELL_TYPE:
        {
            CELL *res = args[0];
            CELL **argv = (CELL **) &args[1];
            CELL *a = array;
            CELL a1;
            CELL *resc;

            for (i = 0; i < columns; i++) {
                int n = 0;

                for (j = 0; j < argc; j++) {
                    if (IS_NULL_C(&argv[j][i]))
                        continue;
                    a[n++] = argv[j][i];
                }

                resc = &res[i];

                if (!n)
                    SET_NULL_C(resc);
                else {
                    qsort(a, n, sizeof(CELL), icmp);
                    *resc = a[n / 2];
                    if ((n & 1) == 0) {
                        a1 = a[(n - 1) / 2];
                        if (*resc != a1)
                            *resc = (*resc + a1) / 2;
                    }
                }
            }

            return 0;
        }
    case FCELL_TYPE:
        {
            FCELL *res = args[0];
            FCELL **argv = (FCELL **) &args[1];
            FCELL *a = array;
            FCELL a1;
            FCELL *resc;

            for (i = 0; i < columns; i++) {
                int n = 0;

                for (j = 0; j < argc; j++) {
                    if (IS_NULL_F(&argv[j][i]))
                        continue;
                    a[n++] = argv[j][i];
                }

                resc = &res[i];

                if (!n)
                    SET_NULL_F(resc);
                else {
                    qsort(a, n, sizeof(FCELL), fcmp);
                    *resc = a[n / 2];
                    if ((n & 1) == 0) {
                        a1 = a[(n - 1) / 2];
                        if (*resc != a1)
                            *resc = (*resc + a1) / 2;
                    }
                }
            }

            return 0;
        }
    case DCELL_TYPE:
        {
            DCELL *res = args[0];
            DCELL **argv = (DCELL **) &args[1];
            DCELL *a = array;
            DCELL a1;
            DCELL *resc;

            for (i = 0; i < columns; i++) {
                int n = 0;

                for (j = 0; j < argc; j++) {
                    if (IS_NULL_D(&argv[j][i]))
                        continue;
                    a[n++] = argv[j][i];
                }

                resc = &res[i];

                if (!n)
                    SET_NULL_D(resc);
                else {
                    qsort(a, n, sizeof(DCELL), dcmp);
                    *resc = a[n / 2];
                    if ((n & 1) == 0) {
                        a1 = a[(n - 1) / 2];
                        if (*resc != a1)
                            *resc = (*resc + a1) / 2;
                    }
                }
            }

            return 0;
        }
    default:
        return E_INV_TYPE;
    }
}