c_median.c

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#include <grass/gis.h>
#include <grass/raster.h>
#include <grass/stats.h>
 
void c_median(DCELL *result, DCELL *values, int n, const void *closure G_UNUSED)
{
    n = sort_cell(values, n);
 
    if (n < 1)
        Rast_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 G_UNUSED)
{
    DCELL total;
    int i;
    DCELL k;
 
    n = sort_cell_w(values, n);
 
    if (n < 1) {
        Rast_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];
}