c_median.c

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#include <grass/gis.h>
#include <grass/stats.h>

void c_median(DCELL * result, DCELL * values, int n, const void *closure)
{
    n = sort_cell(values, n);

    if (n < 1)
        G_set_d_null_value(result, 1);
    else
        *result = (values[(n - 1) / 2] + values[n / 2]) / 2;
}

void w_median(DCELL * result, DCELL(*values)[2], int n, const void *closure)
{
    DCELL total;
    int i;
    DCELL k;

    n = sort_cell_w(values, n);

    if (n < 1) {
        G_set_d_null_value(result, 1);
        return;
    }

    total = 0.0;
    for (i = 0; i < n; i++)
        total += values[i][1];

    k = 0.0;
    for (i = 0; i < n; i++) {
        k += values[i][1];
        if (k >= total / 2)
            break;
    }

    *result = values[i][0];
}